Physics12 Exam Review Questions

Transcription

1 Physics12 Exam Review Questions 1) You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it A) moves along a straight-line path away from the center of the circle. B) moves along a straight-line path toward the center of the circle. C) moves along a straight-line path in its original direction. D) continues to follow a circular path, but with a radius larger than the original radius. E) moves along a path that is neither straight nor circular. 4) When an object moves in uniform circular motion, the direction of its acceleration is A) in the same direction as its velocity vector. B) in the opposite direction of its velocity vector. C) is directed toward the center of its circular path. D) is directed away from the center of its circular path. E) depends on the speed of the object. 7) Two cars go around a banked curve at the proper speed for the banking angle. One car has tires with excellent traction, while the other car has bald slippery tires. Which of these cars is more likely to slide on the pavement as it goes around the curve? A) the car with the new tires B) the car with the bald tires C) Neither car will slide. D) It depends on if the pavement is wet or dry. 10) Two small objects, with masses m and M, are originally a distance r apart, and the gravitational force on each one has magnitude F. The second object has its mass changed to 2M, and the distance is changed to r/4. What is the magnitude of the new gravitational force? A) F/32 B) F/16 C) 16F D) 32F E) 2F 13) An piece of space debris is released from rest at an altitude that is two earth radii from the center of the earth. Compared to its weight on Earth, the weight of this debris is A) zero. B) the same as on the surface of the earth. C) one-half of its weight on the surface of the earth. D) one-third of its weight on the surface of the earth. E) one-quarter of its weight on the surface of the earth. 16) The acceleration due to gravity on Planet A is one-sixth what it is on Planet B, and the radius of the Planet A is one-fourth that of Planet B. The mass of Planet A is what fraction of the mass of Planet B? A) 1/6 B) 1/16 C) 1/24 D) 1/96 E) 1/12 1

2 19) Planet A has twice the mass of Planet B. From this information, what can we conclude about the acceleration due to gravity at the surface of Planet A compared to that at the surface of Planet B? A) The acceleration due to gravity on Planet A must be twice as great as the acceleration due to gravity on Planet B. B) The acceleration due to gravity on Planet A must be four times as great as the acceleration due to gravity on Planet B. C) The acceleration due to gravity on Planet A is the same as the acceleration due to gravity on Planet B. D) The acceleration due to gravity on Planet A is greater than the acceleration due to gravity on Planet B, but we cannot say how much greater. E) We cannot conclude anything about the acceleration due to gravity on Planet A without knowing the radii of the two planets. 22) Satellite A has twice the mass of satellite B, and moves at the same orbital distance from Earth as satellite B. Compare the speeds of the two satellites. A) The speed of B is twice the speed of A. B) The speed of B is one-half the speed of A. C) The speed of B is one-fourth the speed of A. D) The speed of B is equal to the speed of A. E) The speed of B is four times the speed of A. 25) Let the orbital radius of a planet be R and let the orbital period of the planet be T. What quantity is constant for all planets orbiting the sun, assuming circular orbits? A) T/R B) T/R2 C) T2/R3 D) T3/R2 E) T2/R 3) The curved section of a horizontal highway is a circular unbanked arc of radius 740 m. If the coefficient of static friction between this roadway and typical tires is 0.40, what would be the maximum safe driving speed for this horizontal curved section of highway? A) 54 m/s B) 52 m/s C) 50 m/s D) 48 m/s E) 46 m/s 6) A jet plane flying 600 m/s experiences an acceleration of 4.0 g when pulling out of a circular dive. What is the radius of curvature of the circular part of the path in which the plane is flying? A) 640 m B) 1200 m C) 7100 m D) 9200 m 9) A 2.0-kg ball is moving with a constant speed of 5.0 m/s in a horizontal circle whose diameter is 1.0 m. What is the magnitude of the net force on the ball? A) 0 N B) 20 N C) 40 N D) 50 N E) 100 N 2

3 12) A car moving at a steady 10 m/s on a level highway encounters a depression that has a circular cross-section with a radius of 30 m. The car maintains its speed as it drives through the depression. What is the normal force exerted by the seat of the car on a 60.0-kg passenger when the car is at the bottom of the depression? A) 200 N B) 390 N C) 790 N D) 490 N E) 590 N 15) In order to simulate weightlessness for astronauts in training, they are flown in a vertical circle. If the passengers are to experience weightlessness, how fast should an airplane be moving at the top of a vertical circle with a radius of 2.5 km? A) 79 m/s B) 310 m/s C) 260 m/s D) 160 m/s E) 510 m/s 18) A 20-g bead is attached to a light 120 cm-long string as shown in the figure. If the angle α is measured to be 18, what is the speed of the mass? A) 0.55 m/s B) 2.0 m/s C) 3.8 m/s D) 1.3 m/s E) 1.1 m/s 21) A future use of space stations may be to provide hospitals for severely burned persons. It is very painful for a badly burned person on Earth to lie in bed. In a space station, the effect of gravity can be reduced or even eliminated. How long should each rotation take for a doughnut-shaped hospital of 200-m radius so that persons on the outer perimeter would experience 1/10 the normal gravity of Earth? A) 91 min B) 8.7 min C) 4.6 min D) 1.5 min E) min 24) A curved portion of highway has a radius of curvature of 65 m. As a highway engineer, you want to bank this curve at the proper angle for a steady speed of 22 m/s. (a) What banking angle should you specify for this curve? (b) At the proper banking angle, what normal force and what friction force does the highway exert on a 750-kg car going around the curve at the proper speed? Answer: (a) 37 (b) 9200 N (normal force), 0 N (friction) 3

4 27) A highway curve of radius 100 m, banked at an angle of 45, may be negotiated without friction at a speed of A) 22 m/s. B) 31 m/s. C) 44 m/s. D) 67 m/s. 30) What is the magnitude of the gravitational force that two small 7.00-kg balls exert on each other when they are 35.0 cm apart? (G = N m2/kg2) Answer: N 33) A very dense 1500-kg point mass (A) and a dense 1200-kg point mass (B) are held in place 1.00 m apart on a frictionless table. A third point mass is placed between the other two at a point that is 20.0 cm from B along the line connecting A and B. When the third mass is suddenly released, find the magnitude and direction (toward A or toward B) of its initial acceleration. (G = N m2/kg2) Answer: m/s2, toward B 36) At their closest approach, Venus and Earth are m apart. The mass of Venus is kg, the mass of Earth is kg, and G = N m2/kg2. What is the magnitude of the gravitational force exerted by Venus on Earth at that point? A) N B) N C) N D) N E) N 39) What is the distance from the center of the Moon to the point between Earth and the Moon where the gravitational pulls of Earth and Moon are equal? The mass of Earth is kg, the mass of the Moon is kg, the center-to-center distance between Earth and the Moon is m, and G = N m2/kg2. A) m B) m C) m D) m E) m 42) In another solar system, a planet has an airless moon Zygo that is m in diameter. Experiments reveal that a freely falling object at the surface of Zygo accelerates at 0.20 m/s2. What is the mass of Zygo? (G = N m2/kg2) A) kg B) kg C) kg D) kg E) kg 4

5 45) What would be the weight of a 59.1-kg astronaut on a planet twice as massive as Earth and having twice Earth's radius? A) 580 N B) 290 N C) 1160 N D) 118 N E) 1200 N 48) An astronaut goes out for a "space-walk" at a distance above the earth equal to the radius of the earth. What is her acceleration due to gravity at that point? A) zero B) g C) g/2 D) g/4 E) g/ 51) An astronaut drops a marble on the surface of the airless Planet Z-49 and observes that it takes 1.02 s for the marble to fall 2.00 m starting from rest. She also knows that the radius of Z-49 is m. From this information, what will she determine for the mass of Z-49? (G = N m2/kg2) A) 3.30 kg. B) 6.62 kg. C) 4.62 kg. D) 8.09 kg. E) 9.95 kg. 54) By how many newtons does the weight of a 100-kg person decrease when he goes from sea level to mountain top at an altitude of 5000 m? The mean radius of the earth is m. A) 0.60 N B) 1.5 N C) 2.6 N D) 3.6 N E) 9.8 N 57) A 2.10-kg hammer is transported to the Moon. The radius of the Moon is m, its mass is kg, and G = N m2/kg2. How much does the hammer weigh on Earth and on the Moon? Answer: 20.6 N (on Earth), 3.40 N (on the Moon) 60) The captain of a spaceship orbiting planet X discovers that to remain in orbit at from the planet's center, she needs to maintain a speed of What is the mass of planet X? (G = N m2/kg2) A) kg B) kg C) kg D) kg 5

6 65) In another solar system, a planet has a moon that is m in diameter. Measurements reveal that this moon takes 3.0 x 105 s to make each orbit of diameter m. What is the mass of the planet? (G = N m2/kg2) A) kg B) kg C) kg D) kg E) kg 68) A satellite of mass 500 kg orbits the earth with a period of 6,000 s. The earth has a mass of kg, a radius of m, and G = N m2/kg2. (a) Calculate the magnitude of the earth's gravitational force on the satellite. (b) Determine the altitude of the satellite above the earth's surface. Answer: (a) 3900 N (b) m 71) A large telescope of mass 8410 kg is in a circular orbit around the earth, making one revolution every 927 minutes. What is the magnitude of the gravitational force exerted on the satellite by the earth? (G = N m2/kg2, Mearth = kg) Answer: N 74) As you know, the earth has an orbital period of 1.0 year at an orbital radius of 1.0 AU (astronomical unit, the average distance between the earth and the sun). If a new "minor planet" were to be found in a circular orbit with radius 13 AU, what would be its orbital period? Answer: 47 years 77) If NASA wants to put a satellite in a circular orbit around the sun so it will make 2.0 orbits per year, at what distance (in astronomical units, AU) from the sun should that satellite orbit? The earth's orbit is 1.0 AU from the sun. A) 7.6 AU B) 0.63 AU C) 0.50 AU D) 2.0 AU E) 0.71 AU 80) It takes the planet Jupiter 12 years to orbit the sun once in a nearly circular orbit. Assuming that Jupiter's orbit is truly circular, what is the distance from Jupiter to the sun, given that the distance from the earth to the sun is m? A) m B) m C) m D) m E) m 77) In a police ballistics test, a 2.00-g bullet suddenly hits and becomes embedded in a 5.00-kg wood block which is hanging from a 1.20-m long string. This causes the block to swing through an arc of What was the speed of the bullet just before it hit the block? A) 16.7 m/s B) 524 m/s C) 25.3 m/s D) 262 m/s E) 789 m/s 6

7 78) A block of mass m = 9.0 kg and speed V and is behind a block of mass M = 27 kg and speed of as shown int the figure. The surface is frictionless, and the blocks suddenly collide and couple. After the collision, the blocks have a common speed of 0.90 m/s. How much kinetic energy of the blocks is lost due to the collision? A) 8.6 J B) 2.0 J C) 4.6 J D) 11 J E) 31 J 79) As shown in the figure, a bullet of mass kg moving horizontally suddenly strikes a block of wood of mass 1.5 kg that is suspended as a pendulum. The bullet lodges in the wood, and together they swing upward a vertical distance of 0.40 m. The length of the string is 2.0 m. What was the speed of the bullet just before it struck the wooden block? A) 67 m/s B) 250 m/s C) 370 m/s D) 420 m/s E) 650 m/s 6) A croquet mallet balances when suspended from its center of mass, as shown in the left part of the figure. If you cut the mallet into two pieces at its center of mass, as shown in the right part of the figure, how do the masses of the two pieces compare? (There could be more than one correct choice.) A) The masses are equal. B) The piece with the head of the mallet has the greater mass. C) The piece with the head of the mallet has the smaller mass. D) It is impossible to tell., D 2) A 15-kg child is sitting on a playground teeter-totter, 1.5 m from the pivot. What is the minimum distance, on the other side of the pivot, such that a 220-N force will make the child lift off the ground? A) 1.0 m B) 1.5 m C) 0.10 m D) 9.8 m E) 2.4 m 3) An 82-kg painter stands on a long horizontal board 1.55 m from one end. This 27-kg board is uniform, 5.5 m long, and supported at each end by vertical posts. (a) What is the magnitude of the total force provided by both posts? (b) With what force does the post that is closest to the painter push upward on the board? Answer: (a) 1100 N (b) 710 N 7

8 4) An 82-kg diver stands at the edge of a light 5.0-m diving board, which is supported by two vertical pillars that are 1.6 m apart, as shown in the figure. Find the magnitude and direction of the force exerted by each pillar. : 1.7 kn downward, B: 2.5 kn upward 23) A store's sign has a mass of 20 kg and is 3.0 m long. It is uniform, so its center of gravity is at the center of the sign. It is supported horizontally by a small loose bolt attached to the wall at one end and by a wire at the other end, as shown in the figure. What is the magnitude of the net force that the bolt exerts on the sign? A) 460 N B) 230 N C) 200 N D) 120 N E) 300 N 24) A 40-kg uniform ladder that is 5.0 m long is placed against a smooth wall at a height of h = 4.0 m, as shown in the figure. The base of the ladder rests on a rough horizontal surface whose coefficient of static friction with the ladder is An 80-kg bucket is suspended from the top rung of the ladder, just at the wall. What is the magnitude of the force that the ladder exerts on the wall? A) 740 N B) 1300 N C) 980 N D) 900 N E) 1100 N 14) Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are doubled and their separation is also doubled, what happens to the electrical force that each charge exerts on the other one? A) It increases by a factor of 2. B) It increases by a factor of. C) It is reduced by a factor of. D) It increases by a factor of 4. E) It remains the same. 8

9 15) Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are halved and their separation is also halved, what happens to the electrical force that each charge exerts on the other one? A) It increases by a factor of 16. B) It increases by a factor of 8. C) It increases by a factor of 2. D) It increases by a factor of 4. E) It remains the same. 16) Three equal charges +Q are at three of the corners of a square of side d. A fourth charge +Q of equal magnitude is at the center of the square as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the center of the square? A) A B) B C) C D) D 2) A piece of plastic has a net charge of μc. How many more protons than electrons does this piece of plastic have? (e = C) A) B) C) D) E) ) The force of attraction that a μc point charge exerts on a +108 μc point charge has magnitude 4.00 N. How far apart are these two charges? (k = 1/4πε0 = N m2/c2) A) 2.10 m B) 3.67 m C) 3.12 m D) 2.49 m E) 1.13 m 18) Two tiny particles having charges of μc and μc are placed along the x-axis. The µC particle is at x = 0.00 cm, and the other particle is at x = cm. Where on the x-axis must a third charged particle be placed so that it does not experience any net electrostatic force due to the other two particles? A) 4.58 cm B) 45.8 cm C) 50 cm D) 9.12 cm E) 91.2 cm 9

10 28) As shown in the figure, three charges are at the vertices of an equilateral triangle. The charge Q is 6.7 nc, and all the other quantities are accurate to two significant figures. What is the magnitude of the net electric force on the charge Q due to the other two charges? (k = 1/4πε0 = N m2/c2) A) N B) N C) N D) N 47) A small glass bead has been charged to 1.9 nc. What is the strength of the electric field 2.0 cm from the center of the bead? (k = 1/4πε0 = N m2/c2) A) N/C B) N/C C) N/C D) N/C 2) A tiny particle with charge μc is initially moving at 55 m/s. It is then accelerated through a potential difference of 500 V. How much kinetic energy does this particle gain during the period of acceleration? A) J B) J C) 100 J D) 2500 J 14) Two 3.0 μc charges lie on the x-axis, one at the origin and the other at What is the potential (relative to infinity) due to these charges at a point at on the x-axis? (k = 1/4πε0 = N m2/c2) A) 11,000 V B) 9000 V C) 14,000 V D) 3400 V 2) If a charge of 11.4 C passes through a computer in 1.75 min, what is the average current through the computer? Answer: A 14) The current through a piece of lab equipment must be limited to 2.75 A when it is run by a 120-V dc power supply. What must be the resistance of this equipment? Answer: 43.6 Ω 23) A 25-m wire of diameter 0.30 mm draws A when connected across a 3.0-V potential difference. (a) What is the resistance of the wire? (b) What is the resistivity of the material from which the wire is made? Answer: (a) 6.0 Ω (b) Ω m 43) The power rating of a 400-Ω resistor is W. 10

11 (a) What is the maximum safe voltage across this resistor? (b) What is the maximum current the resistor can safely draw? Answer: (a) 17.9 V (b) 44.7 ma 63) How much energy does a 100-W light bulb use in 8.0 hours? A) kwh B) 0.80 kwh C) 13 kwh D) 800 kwh 30) What resistance must be connected in parallel with a 633-Ω resistor to produce an equivalent resistance of 205 Ω? Answer: 303 Ω Var: 1 31) What is the equivalent resistance between points A and B of the network shown in the figure? Answer: 16 Ω Var: 1 32) A combination of a 2.0-Ω resistor in series with 4.0-Ω resistor is connected in parallel with a 3.0-Ω resistor. What is the equivalent resistance of this system? A) 2.0 Ω B) 3.0 Ω C) 4.0 Ω D) 9.0 Ω 68) If V = 40 V and the battery is ideal, what is the potential difference across R1 in the figure? A) 6.7 V B) 8.0 V C) 10 V D) 20 V 11