Academic Challenge District Physics Exam 1996 1. 1.73 seconds after being dropped from rest, a freely-falling object near the Earth's surface will have a speed closest to: (a. ) 17.0 meters per second. (b.) 14.7 meters per second. (c.) 9.80 meters per second. (d.) 5.66 meters per second. (e.) 29.3 meters per second. 2. An electric heater is rated at 500 watts when used in a 110-volt circuit. What is the maximum number of these heaters that can be operated in parallel from the same line without exceeding 40 amperes of current from the line's source? (a.) 10 (b.) 6 (c. ) 8 (d.) 4 (e.) not even 1 3. The distance light travels in one micro-day in vacuum is closest to: (a.) 25 kilometers. (b.) 2.5 gigameters. (c. ) 25 megameters. (d.) 2.5 megameters. (e.) 250 kilometers. 4. If 1.00 ampere of current flows through the 6.00 ohm resistor shown in figure (4. ) what is the value of R? (a.) 2.00 ohms (b.) 12.0 ohms (c.) 6.00 ohms (d. ) 3.00 ohms (e.) none of the above.
5. Identify the missing nuclide in the following reaction: (a.) (b.) (c.) (d.) (e. ) 6. A 1.00 X 10 4 kilogram spaceship is at a distance R from the center of planet X. When exhausting toward the planet at this position, the engine thrust causes the spaceship to have an acceleration of 15.0 meters/second/second away from the planet. When exhausting away from the planet at this position, the same engine thrust causes the spaceship to have an acceleration of 18.0 meters/second/second toward the planet. What is the acceleration due to gravity at this distance from the planet? (a. ) 1.50 meters/second/second (b.) 3.00 meters/second/second (c.) 16.5 meters/second/second (d.) 33.0 meters/second/second (e.) 9.80 meters/second/second 7. A 2.50 gram bullet slug is fired toward a 10.0 kilogram block of wood which is initially at rest on a 'smooth' (frictionless ) horizontal surface. After the slug is imbedded in the block, the slug and block are observed to move with a speed of 60.0 centimeters/second relative to the lab frame. What was the speed of the slug just before it entered the block of wood? (a.) 240. meters/second (b.) 120. meters/second (c.) 3.80 X 10 3 meters/second (d. ) 2.40 X 10 3 meters/second (e.) 38.0 meters/second 8. When a satellite is in an elliptical (non-circular) orbit about the Earth, (a.) the kinetic energy of the satellite and the gravitational potential energy of the Earth-satellite system are both greatest at the greatest distance from the Earth. (b. ) as the kinetic energy of the satellite increases, the gravitational potential energy of the Earth-satellite system decreases. (c.) the gravitational potential energy of the satellite-earth system decreases with increasing separation. (d.) the kinetic energy of the satellite is constant at all points on the orbit. (e.) none of the above are true.
9. The buoyant force acting upon any completely submerged object whose volume is fixed at 1.00 cm 3 depends upon several factors, one of which is: (a.) the density of the object. (b.) the weight of the object. (c.) the mass of the object. (d.) the volume of liquid around the object. (e. ) none of the above. 10. The specific heat of iron is 450. Joules/(kilogram Celsius degree ) How much heat is required to raise the temperature of 40.0 kilograms of iron from 20.0 degrees Celsius to 100.0 degrees Celsius? (a.) 675 Joules (b.) 1.08 x 10 6 Joules (c. ) 1.44 x 10 6 Joules (d.) 900. Joules (e.) none of the above. 11. A net force of "F" accelerates a mass "M" at the rate "a". What will be the acceleration of a mass "M/2" when acted upon by a net force "3F"? (a.) "2a/3" (b.) "a/6" (c.) "2a" (d. ) "6a" (e.) "3a/2" 12. Water has a density of about 1.00 gram per cubic centimeter. The total pressure 12.00 meters below the surface of a lake on Earth: (a.) is about 1.28 x 10 6 Newtons per square meter. (b. ) is about 2.19 x 10 5 Newtons per square meter. (c.) is about 1.18 x 10 6 Newtons per square meter. (d.) depends upon whether the pressure is measured upward or downward at that point. (e.) depends upon the cross-sectional area of the pressure gauge.
13. Aluminum has a specific heat of 900. Joules/(kilogram Celsius degree ) A 2.00 kilogram wedge of aluminum has a speed of 50.0 meters per second just before it strikes and wedges into a stationary tree. Assuming that all of the energy remains with the aluminum in the form of heat energy, how much will its temperature rise? (a.) about 0.14 Celsius degrees (b. ) about 1.4 Celsius degrees (c.) about 0.014 Celsius degrees (d.) about 14 Celsius degrees (e.) about 140 Celsius degrees 14. A bullet has a speed of 300. meters/second and a momentum of 0.600 kilogram meters per second East. The bullet's mass is: (a.) 500. grams. (b.) 1.33 x 10-5 kilograms. (c. ) 2.00 grams. (d.) 180. grams. (e.) none of these. 15. A boyscout carries a 222 Newton backpack on his back. The boyscout moves 10.0 meters along a horizontal surface at constant velocity. The total amount of work that the boyscout has done on the backpack during this process is: (a.) greater than or equal to 200 Joules but less than 2000 Joules (b.) greater than or equal to 0.02 Joules but less than 20 Joules. (c.) greater than or equal to 20 Joules but less than 200 Joules (d. ) less than 0.02 Joules. (e.) greater than or equal to 2000 Joules. 16. In figure (16) shown below, an external force, P, pulls on a 10. kilogram block which is attached to a 20. kilogram block by a light, inextensible cord. No other external forces act upon the system. If the tension, T, in the cord between the two blocks is 10. Newtons, what is the amount of force, P? (a.) 5.0 Newtons (b. ) 15 Newtons (c.) 10. Newtons (d.) 30. Newtons (e.) 20. Newtons
17. A 30.0 centimeter long spring whose mass is negligible is attached at its upper end to a fixed lab support and allowed to hang vertically. When a 20.0 kilogram mass is attached to its lower end, the spring is found to have a new equilibrium length of 36.0 centimeters. The effective spring constant of this spring is between: (a.) 300 Newtons per meter and 600 Newtons per meter. (b.) less than 3 Newtons per meter. (c. ) 3000 Newtons per meter and 6000 Newtons per meter. (d.) 3 Newtons per meter and 6 Newtons per meter. (e.) 30 Newtons per meter and 60Newtons per meter. 18. A rock whose mass is 1.00 kilogram is dropped from rest above the surface of a certain planet. 2.50 seconds later the rock has fallen a distance of 40.0 meters. Assuming that the rock is in free fall the whole time, what is the acceleration due to gravity on this planet? (a.) 64.0 meters per second per second (b. ) 12.8 meters per second per second (c.) 32.0 meters per second per second (d.) 6.40 meters per second per second (e.) 9.80 meters per second per second 19. A boat has a constant velocity of 60.0 miles per hour at 30.0 o North of East. What is the component of this velocity along the direction 10.0 o West of North? (a.) 56.4 miles per hour (b.) 30.0 miles per hour (c.) 38.6 miles per hour (d. ) 20.5 miles per hour (e.) 46.0 miles per hour 20. The steam in a locomotive cylinder whose cross-section is 200. square centimeters causes the piston to be moved outward 2.00 centimeters under an average pressure of 350. Newtons per square centimeter. The work done on the piston by the steam is: (a.) 140,000 Joules (b. ) 1,400 Joules. (c.) 70,000 Joules. (d.) 35,000 Joules. (e.) none of the above.
21. A child sits near the edge of a merry-go-round, making contact only with the floor of the merry-go-round, as it goes round and round with constant angular speed. Ignoring air friction, besides gravity and the normal force between the child and merry-go-round, there is: (a.) no other force acting on the child. (b.) both of the next two forces listed below: (c.) and (d.) (c.) a force on the child directed tangent to the child's orbit in the direction of the child's velocity. (d.) a force on the child directed out from the axel of the merry-go-round. (e. ) a force on the child directed inward toward the axel. 22. A heat engine produces 6284 Joules of heat while performing 2718 Joules of useful work. The efficiency of the engine is: (a. ) 30.2%. (b.) 43.3%. (c.) 56.7%. (d.) 39.6%. (e.) 69.8%. 23. Force, P, pulls on an object whose mass is 2.00 kilogram, causing it to accelerate straight up from the surface of the Earth. When the object has been displaced 5.00 meters by P, the speed of the object has changed from 5.00 meters per second to 10.0 meters per second. How much work has force P done on the object? (a. ) 173 Joules (b.) 198 Joules (c.) 123 Joules (d.) 98.0 Joules (e.) 75.0 Joules 24. An engine operates between 511 degrees Celsius and 273 degrees Celsius. What is the maximum possible efficiency of this engine? (a.) 53.4% (b.) 46.6% (c.) 69.6% (d.) 87.2% (e. ) none of the above
25. A child begins sliding down a 'smooth' playground slide whose shape is parabolic. If the child starts from rest from a height of 3.00 meters, how fast will (s ) be going when (s ) is 0.500 meters above the Earth? (a.) 49.0 meters per second (b. ) 7.00 meters per second (c.) 4.95 meters per second (d.) 7.67 meters per second (e.) More information is required. 26. Considering an organ pipe which is open at both ends, to calculate the approximate frequency of the first vibration mode above the fundamental, one would assume that there are: (a.) 2 displacement antinodes and 1 displacement node (b.) 2 displacement antinodes and 2 displacement nodes (c. ) 3 displacement antinodes and 2 displacement nodes (d.) 3 displacement nodes and 2 displacement antinodes (e.) 1 displacement antinode and 1 displacement node 27. The expression: (kilogram meter per sec per hour) is a unit of: (a.) acceleration (b.) momentum (c.) impulse (d.) angular momentum (e. ) force 28. In a common DC circuit, the speed at which the conduction electrons drift is closest to: (a.) the speed of sound in the wire. (b.) the speed of light. (c.) 10 meters per second. (d.) 1 meter per second. (e. ) 1 centimeter per second. 29. Power could be expressed in units of: (a. ) pound feet per second. (b.) Newton meters. (c.) kilogram meters per second per second. (d.) Joule seconds.
(e.) Watts per second.
30. A 2.50 centimeter high object is placed 80.0 centimeters in front of a concave mirror whose radius of curvature is 60.0 centimeters. The image distance from the lens will be: (a.) 240. centimeters. (b.) 21.8 centimeters. (c. ) 48.0 centimeters. (d.) 34.3 centimeters. (e.) none of the above. 31. A truck tire is filled to an absolute pressure of 2.00 atmospheres at a temperature of 283 Kelvin. After driving some distance, the temperature of the tire has risen to 313 Kelvin. Assuming that the volume change of the tire is negligible, what is the absolute pressure in the tire at the higher temperature? (a.) 2.32 atm. (b.) 8.00 atm. (c.) 2.11 atm. (d. ) 2.21 atm. (e.) 3.32 atm. 32. Two small, charged particles exert a repulsive force of 0.600 Newtons on each other. The force that they exert on each other if they are only 1/6 as far apart is about: (a. ) 21.6 Newtons. (b.) 3.60 Newtons. (c.) 0.100 Newtons. (d.) 0.0167 Newtons. (e.) 38.4 Newtons. 33. Steel has a coefficient of linear expansion of about 12.0 x 10-6 per Celsius degree. If a precise steel tape measure has been accurately calibrated at 20.0 degrees Celsius, what will the percentage error in a reading be at 50.0 degrees Celsius? Let a positive percent indicate too great a reading and vice versa. (a. ) -0.036 % (b.) -0.06 % (c.) +0.06 %. (d.) +0.036 %. (e.) The answer cannot be determined without knowing the initial reading.
34. A spaceship moves directly toward you with a speed, relative to you, of 1/4 the speed of light. The spaceship turns on a laser beam, also directed at you. Relative to you, the speed of the laser beam would be: (a.) 3/4 the speed of light. (b.) 5/4 the speed of light. (c.) the speed of sound. (d.) very much dependent upon the frequency of the light. (e. ) equal to the speed of light. 35. The intensity of sound could be measured in units of: (a.) Newtons per second per cubic meter. (b.) Joule seconds per meter per meter. (c.) Watts. (d. ) Watts per meter per meter. (e.) none of the above. 36. An ideal transformer takes a voltage of 170 V sin( 377t rad/s) at its primary and produces a secondary voltage of 35.5 V sin(377t rad/s ) The ratio of secondary current to primary current is: (a. ) 4.79. (b.) 1.00. (c.) 0.209. (d.) 22.9. (e.) 0.0437. 37. A plot of velocity versus time for a 20.0 kilogram object is shown in figure (37 ) What is the net force acting on the object at t=4.00 seconds? (a.) 10 N North (b. ) 200 N South (c.) 800 N South (d.) 800 N North (e.) None of the above are correct.
38. A nearsighted eye has a near point of 12.0 centimeters and a far point of 115 centimeters. Assuming that the lens is 2.00 centimeters from the eye, what lens power is required for the eye to see distant objects clearly? (a.) -0.870 D (b.) -8.33 D (c.) -10.0 D (d.) -0.785 D (e. ) -0.885 D 39.Carbon-14 has a half-life of 5730 years. If you start with a sample of 1,000,000 carbon-14 atoms, approximately how many will have decayed after 11460 years? (a.) All of them decay. (b.) 250,000 (c.) 865,000 (d. ) 750,000 (e.) 135,000 40. One object has a mass of 2.0 kilograms and a velocity of 4.0 meters per second East. A second object has a mass of 1.0 kilogram and a velocity of 8.0 meters per second West. (a.) The two masses have the same momentum and kinetic energy. (b.) The two masses have the same momentum, but the 1.0 kilogram mass has greater kinetic energy. (c.) The 1.0 kilogram mass has less kinetic energy than the 2.0 kilogram mass. (d.) The total momentum of the two masses has a value of 16 kilogram meters per second along the East-West direction. (e. ) None of the above are correct.