(01) The force of gravitational attraction is represented by the equation

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1 (01) The force of gravitational attraction is represented by the equation Gm1m 2 F, 2 r where F is the magnitude of the gravitational attraction on either body, m 1 and m 2 are the masses of the bodies, r is the distance between them, and G is the gravitational constant. In SI units, the units for force are kg m/s 2, the units of mass are kg, and the units of distance are m. For this equation to have consistent units, the units of G must be which of the following? (2 marks) A. 3 kg 2 m s B. kg s m C. 3 m 2 kg s D. m 2 kg s 3 2 (02) Expressed with the correct number of significant figures, what is the volume of a rectangular room that measures m by m by 9.50 m? A m 3 B m 3 C m 3 D m 3 (03) A child throws a baseball directly upward. What are the signs of the velocity and acceleration of the ball at the very top of the ball's motion (i.e., the point of maximum height)? (The positive y axis is upward.) velocity acceleration A. + B. 0 C. + D. 0

2 (04) A graph of position as a function of time for a particle traveling along a straight line is shown below. Which of the graphs shown is the correct v vs. t plot for the motion described in the graph? C. C D. D (05) Consider an object sliding on a frictionless ramp as depicted r here. Which direction best approximates the direction of a when the object is at position 2? A. Straight up B. Upward to the right C. Straight down D. Downward to the left

3 (06) Consider an object sliding on a frictionless ramp as depicted r here. Which direction best approximates the direction of a when the object is at position 3? A. Straight up B. Upward to the right C. Straight down D. Downward to the left Use the statement and figure below to answer the next two questions (06 and 13). A battleship simultaneously fires two shells toward two identical enemy ships. One shell hits ship A, which is close by, and the other hits ship B, which is farther away. The two shells are fired at the same speed. Assume that air resistance is negligible and that the magnitude of the acceleration due to gravity is g. (07) What shape is the trajectory (graph of y vs. x) of the shells? A. Straight line B. Parabola C. Hyperbola D. The shape cannot be determined (08) For two shells fired at the same speed which statement about the horizontal distance travelled is correct? A. The shell fired at a larger angle with respect to the horizontal lands farther away. B. The shell fired at an angle closest to 45 degrees lands farther away. C. The shell fired at a smaller angle with respect to the horizontal lands farther away. D. The lighter shell lands farther away. (09) Which shell is fired at the larger angle? C. Both shells are launched with the same horizontal velocity. D. Not enough information to determine. (10) Which shell is launched with a greater vertical velocity, v y? C. Both shells are launched with the same horizontal velocity. D. Not enough information to determine.

4 (11) Which shell is launched with a greater horizontal velocity, v x? C. Both shells are launched with the same horizontal velocity. D. Not enough information to determine. (12) Which shell reaches the greater maximum height? C. Both shells are launched with the same horizontal velocity. D. Not enough information to determine. (13) Which shell has the longest travel time (time elapsed between being fired and hitting the enemy ship)? C. Both shells are launched with the same horizontal velocity. D. Not enough information to determine. (14) If a car is moving to the left with constant velocity, one can conclude that A. there must be no forces applied to the car. B. the net force applied to the car is directed to the left. C. the net force applied to the car is zero. D. there is exactly one force applied to the car. (15) An object cannot remain at rest unless A. there are no forces at all acting on it. B. the net force acting on it is zero. C. the net force acting on it is constant. D. there is only one force acting on it. (16) An object will have constant acceleration if A. there are no forces at all acting on it. B. the net force acting on it is zero. C. the net force acting on it is constant in magnitude and direction. D. there is only one force acting on it.

5 (17) According to Newton's 3rd law, the force on the (smaller) moon due to the (larger) earth is A. greater in magnitude than, and in the opposite direction from, the force on the earth due to the moon. B. greater in magnitude than, and in the same direction as, the force on the earth due to the moon. C. equal in magnitude to, and in the opposite direction from, the force on the earth due to the moon. D. equal in magnitude to, and in the same direction as, the force on the earth due to the moon. (18) A 6-kg bucket of water is being pulled straight up by a string at a constant speed. What is the tension in the rope? A. about 42 N B. about 60 N C. about 78 N D. 0 N because the bucket has no acceleration (19) At a certain point the speed of the bucket begins to change. The bucket now has an upward constant acceleration of magnitude 3 m/s 2. What is the tension in the rope now? A. about 42 N B. about 60 N C. about 78 N D. It is increasing as the speed increases. (20) Now assume that the bucket has a downward acceleration, with a constant acceleration of magnitude 3 m/s 2. Now what is the tension in the rope? A. about 42 N B. about 60 N C. about 78 N D. It is decreasing as the speed increases.

6 Use the statement and figure below to answer the next two questions (21 and 26). Two blocks are stacked on top of each other on the floor of an elevator. For each of the following situations, select the correct relationship between the magnitudes of the two forces given. (21) The elevator is moving downward at a constant speed. The magnitude of the force of the bottom block on the top block is A. greater than B. less than C. equal to D. unknown compare to the magnitude of the force of the earth on the top block. (22) The elevator is moving downward at a constant speed. The magnitude of the force of the bottom block on top block is A. greater than B. less than C. equal to D. unknown compare to the magnitude of the force of the top block on bottom block. (23) The elevator is moving downward at an increasing speed. The magnitude of the force of the bottom block on the top block is A. greater than B. less than C. equal to D. unknown compare to the magnitude of the force of the earth on the top block. (24) The elevator is moving downward at an increasing speed. The magnitude of the force of the bottom block on top block is A. greater than B. less than C. equal to D. unknown compare to the magnitude of the force of the earth on the top block.

7 (25) The elevator is moving upward. The magnitude of the force of the bottom block on the top block is A. greater than B. less than C. equal to D. unknown compare to the magnitude of the force of the earth on the top block. (26) The magnitude of the force of the bottom block on top block is A. greater than B. less than C. equal to D. unknown compare to the magnitude of the force of the top block on bottom block. (27) When a board with a box on it is slowly tilted to a larger and larger angle, common experience shows that the box will at some point "break loose" and start to accelerate down the board. The box begins to slide once the component of its weight parallel to the board, w, equals the maximum force of static friction. Which of the following is the most general explanation for why the box accelerates down the board after it begins to slide (rather than sliding with constant speed)? A. Once the box is moving, w is less than the force of static friction but greater than the force of kinetic friction. B. Once the box is moving, w is greater than the force of static friction but less than the force of kinetic friction C. The coefficient of kinetic friction is less than the coefficient of static friction. D. When the box is stationary, w equals the force of static friction, but once the box starts moving, the sliding reduces the normal force, which in turn reduces the friction

8 Use the statements and figure below to answer the next two questions (28 and 29) In the situation shown in the figure, a person is pulling with a constant, nonzero force F on string 1, which is attached to block A. Block A is also attached to block B via string 2, as shown. For this problem, assume that neither string stretches and that friction is negligible. Both blocks have finite (nonzero) mass. (28) Which one of the following statements correctly describes the relationship between the accelerations of blocks A and B? A. Block A has a larger acceleration than block B. lock B has a larger acceleration than block A C. Both blocks have the same acceleration. D. More information is needed to determine the relationship between the accelerations (29) How does the magnitude of the tension in string 1, T 1, compare with the tension in string 2, T 2? A. T1 T2 B. T1 T2 C. T1 T2 D. More information is needed to determine the relationship between T1 and T 2. (30) An object cannot remain at rest unless which of the following holds? A. The net force acting on it is zero. B. The net force acting on it is constant and nonzero. C. There are no forces at all acting on it. D. There is only one force acting on it. (31) If a block is moving to the left at a constant velocity, what can one conclude? A. There is exactly one force applied to the block. B. The net force applied to the block is directed to the left. C. The net force applied to the block is zero. D. There must be no forces at all applied to the block.

9 (32) A block of mass 2 kg is acted upon by two forces: 3 N(directed to the left) and 4 N(directed to the right). What can you say about the block's motion? A. It must be moving to the left. B. It must be moving to the right. C. It must be at rest. D. It could be moving to the left, moving to the right, or be instantaneously at rest. (33) A massive block is being pulled along a horizontal frictionless surface by a constant horizontal force. The block must be. A. continuously changing direction B. moving at constant velocity C. moving with a constant nonzero acceleration D. moving with continuously increasing acceleration (34) Two forces, of magnitude 4N and 10N, are applied to an object. The relative direction of the forces is unknown. The net force acting on the object. A. cannot be equal to 5 N B. cannot be equal to 10 N. C. cannot be directed the same way as the force of 10 N. D. must be greater than 10 N.

10 Use the statements and figure below to answer the next two questions (35 and 36). A small metal cylinder rests on a circular turntable that is rotating at a constant rate, as illustrated in the diagram. (35) Which of the following sets of vectors best describes the velocity, acceleration, and net force acting on the cylinder at the point indicated in the diagram? A. a B. b C. c D. d (36) Let R be the distance between the cylinder and the centre of the turntable. Now assume that the cylinder is moved to a new location R/2 from the centre of the turntable. Which of the following statements accurately describe the motion of the cylinder at the new location? (i) The speed of the cylinder has decreased. (ii) The speed of the cylinder has increased. (iii) The magnitude of the acceleration of the cylinder has decreased (iv) The magnitude of the acceleration of the cylinder has increased. A. (i) and (iii) B. (ii) and (iv) C. (i) and (iv) D. (ii) and (iii)

11 (37) A car of mass M = 900 kg travelling at 65.0 km/hour enters turn. The road is level (angle = 0 ), and the coefficient of static friction between the road and the car's tires is. Which of the following diagrams represents the forces acting on the car as it goes around the curve? F fr represents the friction force. C. C D. D Use the statements and figure below to answer the next two questions (38 and 40). Two blocks of ice, one four times as heavy as the other, are at rest on a frozen lake. A person pushes each block the same distance d. Ignore friction and assume that an equal force F is exerted on each block. (38) Which of the following statements is true about the kinetic energy of the heavier block after the push? A. It is smaller than the kinetic energy of the lighter block. B. It is equal to the kinetic energy of the lighter block. C. It is larger than the kinetic energy of the lighter block. D. It cannot be determined without knowing the force and the mass of each block (39) Compared to the speed of the heavier block, how fast does the light block travel? A. one quarter as fast B. half as fast C. the same speed D. twice as fast

12 (40) Now assume that both blocks have the same speed after being pushed with the same force F. What can be said about the distances the two blocks are pushed? A. The heavy block must be pushed 16 times farther than the light block. B. The heavy block must be pushed 4 times farther than the light block. C. The heavy block must be pushed 2 times farther than the light block. D. The heavy block must be pushed the same distance as the light block. Use the statements and figure below to answer the next two questions (41 and 42). As illustrated in the figure, a spring with spring constant k is stretched from x = 0 to x = 3d, where x = 0 is the equilibrium position of the spring. (41) During which interval is the largest amount of energy required to stretch the spring? A. From x = 0 to x = d B. From x = d to x = 2d C. From x = 2d to x = 3d D. The energy required is the same in all three intervals (42) Consider two springs A and B that are attached to a wall. Spring A has a spring constant that is four times that of the spring constant of spring B. If the same amount of energy is required to stretch both springs, what can be said about the distance each spring is stretched? A. Spring A must stretch 4 times as far as spring B B. Spring A must stretch 2 times as far as spring B. C. Spring A must stretch the same distance as spring B. D. Spring A must stretch half the distance spring B stretches.

13 (43) Two identical springs are attached to two different masses, M A and M B, where M A is greater than M B. The masses lie on a frictionless surface. Both springs are compressed the same distance, d, as shown in the figure. Which of the following statements describes the energy required to compress spring A and spring B? A. Spring A requires more energy than spring B. B. Spring A requires the same amount of energy as spring B. C. Spring A requires less energy than spring B. D. Not enough information is provided to answer the question Use the statements and figure below to answer the next two questions (44 and 46). Consider an object launched vertically upward with an initial speed v. Neglect air resistance. (44) As the projectile goes upward, what energy changes take place? A. Both kinetic and potential energy decrease. oth kinetic and potential energy increase. C. Kinetic energy decreases; potential energy increases. D. Kinetic energy increases; potential energy decreases (45) At the top point of the flight, what can be said about the projectile's kinetic and potential energy? A. Both kinetic and potential energy are at their maximum values. oth kinetic and potential energy are at their minimum values. C. Kinetic energy is at a maximum; potential energy is at a minimum. D. Kinetic energy is at a minimum; potential energy is at a maximum (46) The potential energy of the object at the moment of launch. A. is negative B. is positive C. is zero D. depends on the choice of the "zero level" of potential energy

14 Use the statements and figure below to answer the next two questions (47 and 48). Balls A and B roll across a table, then collide and bounce off each other. The paths of the two balls are pictured (viewed from above) in the diagram. (47) Which set of arrows best represents the change in momentum for balls A and B? C. C D. D (48) Which of the following arrows indicates the direction of the impulse applied to ball A by ball B? C. C D. D (49) A bullet of mass m b is fired horizontally with speed v 1 at a wooden block of mass m w resting on a frictionless table. The bullet hits the block and becomes completely embedded within it. After the bullet has come to rest within the block, the block, with the bullet in it, is travelling at speed v f. Which of the following quantities, if any, are conserved during this collision? A. kinetic energy only B. momentum only C. kinetic energy and momentum D. neither momentum nor kinetic energy

15 Use the statements and figure below to answer the next two questions (50 and 52). An object of mass m is attached to a vertically oriented spring. The object is pulled a short distance below its equilibrium position and released from rest. Set the origin of the coordinate system at the equilibrium position of the object and choose upward as the positive direction. Assume air resistance is so small that it can be ignored. (50) Beginning the instant the object is released, select the graph that best matches the position vs. time graph for the object. A. E B. F C. G D. H (51) Beginning the instant the object is released, select the graph that best matches the velocity vs. time graph for the object. A. E B. F C. G D. H (52) Beginning the instant the object is released, select the graph that best matches the acceleration vs. time graph for the object. A. E B. F C. G D. H

16 Use the statements and figure below to answer the next two questions (53 and 58). Consider a harmonic oscillator at four different moments, labelled A, B, C, and D, as shown in the figure. Assume that the force constant k, the mass of the block, m, and the amplitude of vibrations, A, are given. Answer the following questions. (53) Which moment corresponds to the maximum potential energy of the system? C. C D. D (54) Which moment corresponds to the minimum kinetic energy of the system? C. C D. D (55) Consider the block in the process of oscillating. If the kinetic energy of the block is increasing, the block must be A. moving to the right. B. moving to the left. C. moving away from equilibrium. D. moving toward equilibrium (56) Which moment corresponds to the maximum kinetic energy of the system? C. C D. D

17 (57) Which moment corresponds to the minimum potential energy of the system? C. C D. D (58) At which moment is K = U? C. C D. D Use the statements and figure below to answer the next two questions (59 and 61). A simple pendulum consisting of a bob of mass m attached to a string of length L swings with a period T. (59) If the bob's mass is doubled, approximately what will the pendulum's new period be? A. T /2 B. T C. 2T D. 2T (60) If the pendulum is brought on the moon where the gravitational acceleration is about g/6, approximately what will its period now be? A. T /6 B. T / 6 C. 6T D. 6T (61) If the pendulum is taken into the orbiting space station what will happen to the bob? A. It will continue to oscillate in a vertical plane with the same period. B. It will no longer oscillate because there is no gravity in space. C. It will no longer oscillate because both the pendulum and the point to which it is attached are in free fall. D. It will oscillate much faster with a period that approaches zero.

18 Use the statements and figure below to answer the next two questions (62 and 65). While working on her bike, Amanita turns it upside down and gives the front wheel a counter clockwise spin. It spins at approximately constant speed for a few seconds. During this portion of the motion, she records the x and y positions and velocities, as well as the angular position and angular velocity, for the point on the rim designated by the yellow-orange dot in the figure. Let the origin of the coordinate system be at the centre of the wheel, the positive x direction to the right, the positive y position up, and the positive angular position counter clockwise. The graphs begin when the point is at the indicated position. One graph may be the correct answer to more than one part. (62) Which of the graphs corresponds to x position versus time? A. E B. F C. G D. H (63) Which of the graphs corresponds to angular position versus time? C. C D. D

19 (64) Which of the graphs corresponds to y velocity versus time? A. E B. F C. G D. H (65) Which of the following graphs corresponds to angular velocity versus time? C. C D. D (66) The artist Anya Calderona constructs the mobile shown in the figure. In the illustrated configuration, the mobile is perfectly balanced. If Anya decides to make the star twice as massive, and not change the length of any crossbar or the location of any object, what does she have to do with the mass of the smiley face to keep the mobile in perfect balance? Note that she may have to change masses of other objects to keep the entire structure balanced. A. make it eight times more massive B. make it four times more massive C. make it twice as massive D. impossible to tell (67) Ten identical steel wires have equal lengths L and equal "spring constants" k. The wires are connected end to end, so that the resultant wire has length 10L. What is the "spring constant" of the resulting wire? A. 0.1 k B. k C. 10k D. 100k (68) Ten identical steel wires have equal lengths L and equal "spring constants" k. The wires are slightly twisted together, so that the resultant wire has length L and is 10 times as thick as each individual wire. What is the "spring constant" of the resulting wire? A. 0.1 k B. k C. 10k D. 100k

20 Use the statements and figure below to answer the next two questions (69 and 70). The pressure at 10 m below the surface of the ocean is about Pa. (69) Which of the following statements is true? A. The weight of a column of seawater 1 m 2 in cross section and 10 m high is about N. B. The weight of a column of seawater 1 m 2 in cross section and 10 m high plus the weight of a column of air with the same cross section extending up to the top of the atmosphere is about N. C. The weight of 1 m 3 of seawater at 10 m below the surface of the ocean is about N. D. The density of seawater is about times the density of air at sea level (70) Now consider he pressure at 20 m below the surface of the ocean. A. twice that at a depth of 10 m. B. the same as that at a depth of 10 m. C. equal to that at a depth of 10 m plus the weight of a column of seawater 1 m 2 in cross section and 10 m high. D. equal to the weight of a column of seawater 1 m 2 in cross section and 20 m high (71) Consider the following statement: The magnitude of the buoyant force is equal to the weight of fluid displaced by the object. Under what circumstances is this statement true? A. for every object submerged partially or completely in a fluid B. only for an object that floats C. only for an object that sinks D. for no object submerged in a fluid (72) Consider the following statement: The magnitude of the buoyant force is equal to the weight of the amount of fluid that has the same total volume as the object. Under what circumstances is this statement true? A. for every object submerged partially or completely in a fluid B. only for an object that floats C. only for an object that sinks D. for no object submerged in a fluid

21 (73) Consider the following statement: The magnitude of the buoyant force equals the weight of the object. Under what circumstances is this statement true? A. for every object submerged partially or completely in a fluid B. only for an object that floats C. only for an object that sinks D. for no object submerged in a fluid (74) Consider the following statement: The magnitude of the buoyant force is less than the weight of the object. Under what circumstances is this statement true? A. for every object submerged partially or completely in a fluid B. only for an object that floats C. only for an object that sinks D. for no object submerged in a fluid (75) An object is floating in equilibrium on the surface of a liquid. The object is then removed and placed in another container, filled with a denser liquid. What would you observe? A. The object would sink all the way to the bottom. B. The object would float submerged more deeply than in the first container. C. The object would float submerged less deeply than in the first container. D. More than one of these outcomes is possible. (76) An object is floating in equilibrium on the surface of a liquid. The object is then removed and placed in another container, filled with a less dense liquid. What would you observe? A. The object would sink all the way to the bottom. B. The object would float submerged more deeply than in the first container. C. The object would float submerged less deeply than in the first container. D. More than one of these outcomes is possible.

22 Use the statements and figure below to answer the next two questions (77 and 78). A rectangular wooden block of weight W floats with exactly one-half of its volume below the waterline. (77) What is the buoyant force acting on the block? A. 2W B. W C. 1/2W D. The buoyant force cannot be determined (78) The density of water is 1.00 g/cm 3. What is the density of the block? A. between 1.00 and 2.00 g/cm 3 B g/cm 3 C. between 1.00 and 2.00 g/cm 3 D g/cm 3 (79) Masses are stacked on top of the block until the top of the block is level with the waterline. This requires 20 g of mass. What is the mass of the wooden block? A. 40 g B. 20 g C. 10 g D. 5 g

23 Use the statements and figure below to answer the next two questions (80 and 81). A flask of water rests on a scale that reads 100 N. Then, a small block of unknown material is held completely submerged in the water. The block does not touch any part of the flask, and the person holding the block will not tell you whether the block is being pulled up (keeping it from falling further) or pushed down (keeping it from bobbing back up). (80) What is the new reading on the scale? A. greater than 100 N B. 100 N C. less than 100 N D. It is impossible to determine (81) A certain sound contains the following frequencies: 400 H z, 1600 H z, and 2400 H z. Select the best description of this sound. A. This is a pure tone. B. This is a complex tone with a fundamental of 400 H z, plus some of its overtones. C. This is a complex tone with a virtual pitch of 800 H z. D. These frequencies are unrelated, so they are probably pure tones from three different sound sources

24 (82) Two sources of coherent radio waves broadcasting in phase are located as shown below. Each grid square is 0.5 m square, and the radio sources broadcast at = 2.0 m. At Point A and Point B are the interference between the two sources constructive or destructive? Point A Point B A. constructive constructive B. constructive destructive C. destructive constructive D. destructive destructive (83) Which of the following statement correctly describe a sound wave? A. propagation of sound particles that are different from the particles that comprise the medium B. Propagation of energy that does not require a medium C. Propagation of pressure fluctuations in a medium D. Propagation of energy that passes through empty spaces between the particles that comprise the medium

25 Use the statements and figure below to answer the next two questions (84 and 86). An open organ pipe (i.e., a pipe open at both ends) of length L 0 has a fundamental frequency f 0. (84) If the organ pipe is cut in half, what is the new fundamental frequency? A. 4f 0 B. 2f 0 C. f 0 /2 D. f 0 /4 (85) After being cut in half in Part A, the organ pipe is closed off at one end. What is the new fundamental frequency? A. remains unchanged B. 2f 0 C. f 0 D. f 0 /2 (86) The air from the pipe in Part B (i.e., the original pipe after being cut in half and closed off at one end) is replaced with helium. (The speed of sound in helium is about three times faster than in air.). What is the approximate new fundamental frequency? A. 3f 0 B. 2f 0 C. f 0 D. remain unchanged (87) A square is cut out of a copper sheet. The square is heated uniformly. As a result, it turns into A. a square with a larger area B. a square with a smaller area C. a rectangle with a larger area D. a rectangle with a smaller area (88) A square is cut out of a copper sheet. Two straight scratches on the surface of the square intersect forming an angle. The square is heated uniformly. As a result, the angle between the scratches A. increases B. decreases C. stays the same D. The answer depends on whether is an acute or obtuse angle (89) A square is cut out of a copper sheet. A circular hole is drilled in the square. The square is heated uniformly. As a result, the diameter of the hole A. increases B. decreases C. stays the same D. The answer depends on the size of the hole

26 (90) You fill your car tires with air on a cold morning (0 C) to a gauge pressure of 210 kpa. As you drive, friction and the warming day increase the air temperature inside the tire to 35 C, while the volume remains constant. What's the new gauge pressure? A. 226 kpa B. 210 kpa C. 237 kpa D. 253 kpa (91) What's the thermal energy of one mole of ideal gas at 7 C? A. 87 J B J C J D J (92) The specific heat capacity of aluminium is about twice that of iron. Consider two blocks of equal mass, one made of aluminium and the other one made of iron, initially in thermal equilibrium. Heat is added to each block at the same constant rate until it reaches a temperature of 500 K. Which of the following statements is true? A. There is not enough information to determine which block reach the final temperature first. B. The two blocks take the same amount of time to reach the final temperature. C. The aluminium takes less time than the iron to reach the final temperature. D. The iron takes less time than the aluminium to reach the final temperature. (93) In an insulated vessel, a quantity of hot water at temperature T 1 is mixed with a different quantity of cold water at temperature T 2. After equilibrium is established, the vessel contains. A. steam only B. ice only C. water and ice D. water only (94) The final temperature of the water is. A. higher than T 1 B. between T 1 and T 2 C. lower than T 2 D. There is not enough information to determine the final temperature.

27 (95) In an insulated container, liquid water is mixed with ice. What can you conclude about the phases present in the container when equilibrium is established? A. There would be ice only. B. There would be liquid water only. C. There would be both ice and liquid water. D. There is no way of knowing the phase composition without more information (96) Assume that water and steam, initially at 100 C, are cooled down to skin temperature, 34 C, when they come in contact with your skin. Assume that the steam condenses extremely fast. We will further assume a constant specific heat capacity c = 4190 J/(kg K) for both liquid water and steam. A. Steam burns the skin worse than hot water because the thermal conductivity of steam is much higher than that of liquid water. B. Steam burns the skin worse than hot water because the latent heat of vaporization is released as well. C. Hot water burns the skin worse than steam because the thermal conductivity of hot water is much higher than that of steam. D. Hot water and steam both burn skin about equally badly (97) Conduction the flow of heat from a hotter object to a cooler object or from a hotter region to a cooler region of the same object is the most common mechanism of heat transfer. The formula governing this is Q TH TC H ka t L where H is known as the heat current. This formula applies to. A. any object of cross-sectional area A, length L, and thermal conductivity k. B. any object of cross-sectional area A, length L, and thermal resistivity k. C. a plate of surface area A, long dimension L, and thermal conductivity k. D. a plate of surface area A, long dimension L, and thermal resistivity k.