32 Solved Problems on Kinetic Energy and Electromagnetic Waves - Exam | PHYS 101, Exams of Physics

Download 32 Solved Problems on Kinetic Energy and Electromagnetic Waves - Exam | PHYS 101 and more Exams Physics in PDF only on Docsity! PHYS101 Sec 001 Hour Exam No. 3 Page: 1 PHYS101 Sec 001 Hour Exam No. 3 Page: 2 1 The starship Enterprise is travelling on impulse drive at 4/5 light speed. For every two minutes that pass on board the ship, a clock back on earth will read an interval close to a. two minutes. b. three minutes and twenty seconds. c. two minutes and ten seconds. d. two minutes and thirty seconds. 2 Two spaceships y side by side at nearly the speed of light, separated by a distance of 186,000 miles (one light-second in other words) in their own reference frame. If radio messages are exchanged between the ships the clocks on board the ships will nd that each exchange is delayed by a round-trip travel time of a. less than 2s. b. 2s. c. more than 2s. d. an indeterminate amount of time. 3 The force on a 5kg object in a gravitational eld whose magnitude is 4m/s2 is equal to a. 20N. b. 4N. c. 50N. d. 5N. e. 6N. 4 An aircraft carrier uses a catapult to launch airplanes from its deck. The catapult consists of a hook that runs along a slot in the deck. The airplane is attached to the hook and is pulled along the slot until it reaches take-off speed. Suppose that the catapult accelerates the plane at 5 times the acceleration of gravity (5 “g”s) and the take-off speed is 100m/s. How long must the slot in the deck be? a. 1000m. b. 200m. c. 1m. d. 10m. e. 100m. 5 A 2kg rock is dropped from rest at a height of 30 meters above the ground. How much heat energy is generated when it hits the ground? a. 600J. b. 900J. c. 0. d. 60J. PHYS101 Sec 001 Hour Exam No. 3 Page: 5 18 A rogue star is observed to be headed directly for our sun. The expected collision will cause a supernova explosion with an initial are of electromagnetic radiation capable of destroying everything in its path. Before the collision occurs, you get into a spaceship and speed away at 185,000 miles per second (relative to the sun). As you race away from the sun, the predicted supernova explosion occurs and sends its initial are after you at 186,000 miles per second (relative to the former sun). As each second passes inside the ship, the distance between you and the are closes (relative to the ship) by a. 186,000 miles. b. 185,000 miles. c. 1000 miles. d. 187,000 miles. e. 2000 miles. 19 Maxwell's derivation of the speed of light from physical laws was a problem for his fellow scientists because a. It violated velocity addition. b. They disbelieved some steps in the derivation. c. It violated energy conservation. d. The speed was not what they expected. 20 An automobile bumper jack moves the bumper up a distance of 0:01m (one centimeter) for every meter that the jack handle is moved downward. It is found that a force of 133N on the jack handle produces a lifting force of 10; 000N on the bumper. What is the efciency of this jack? a. 50%. b. 66%. c. 100%. d. 75%. 21 If the speed of an automobile increases by a factor of two, the distance that it takes to stop should increase by a factor of a. 4. b. 3. c. 2: d. 16: e. 9. 22 In the aether theory of light, a pulse of light travels at 186,000 miles per second relative to a. the aether. b. any inertial reference frame. c. the observer of the light. d. the source of the light. PHYS101 Sec 001 Hour Exam No. 3 Page: 6 23 A spaceship travels from the earth to a star that is 12 light years away. If the trip takes 13 years in earth time, how many years pass on board the ship? a. 4. b. 3. c. 2. d. 6. e. 5. 24 Suppose that observers on Earth nd that an asteroid collides with the planet Mars at exactly the same time that a comet collides with the earth. If a spaceship ying from Earth toward Mars observes these catastrophes, it will calculate that a. Mars get hit before the earth does. b. Earth get hit before Mars does. c. both happen at the same time. 25 In one experiment, two spheres, one with a mass of 1kg and the other with a mass of 1000kg are separated by one meter and attract each other with a tiny force. If the spheres are then replaced by one with a mass of 3kg and one with a mass of 2000kg, still one meter apart, the force between the masses will be a. the same as in the rst experiment. b. three times the force in the rst experiment. c. six times the force in the rst experiment. d. twice the force in the rst experiment. 26 In a spacetime diagram with t the time and x the distance, all of the points on the space axis have a. x = 0. b. t = x. c. t = x = 0. d. t = 0. 27 Suppose that two objects, each with the same mass, are accelerated from rest to the same velocity. The force that accelerates one object is much larger than the force that accelerates the other object but acts for a shorter time. The work done by the larger force is a. smaller than the work done by the smaller force. b. equal to the work done by the smaller force. c. larger than the work done by the smaller force. d. unrelated to the work done by the smaller force. PHYS101 Sec 001 Hour Exam No. 3 Page: 7 28 If the earth were compressed to the size of the moon — a factor of four in radius — with no change in its mass, the weight of a 100kg object on its surface would then be a. 1000N. b. 250N. c. 4000N. d. 16000N. e. 125N. 29 The following spacetime diagram uses c=1 units. Which is the world-line of an object at rest? 30 Two spaceships travel, side-by-side, at nearly the speed of light (relative to the earth). Each ship sees the other just 0.1 light-years away in a direction perpendicular to their direction of motion. Each ship leaves a thin trail of gas as it travels. In a frame of reference at rest relative to the earth, the distance between the two gas trails will be a. 0.1 light years. b. less than 0.1 light years. c. more than 0.1 light years. 31 A complicated system of pulleys and gears is set up so that pulling down on an “input” rope by one meter causes an “output” rope to move upward by 1/5 meter. If a force of 10 newtons is applied to the input rope, how much force can the output rope exert? a. 50N. b. 5N. c. 2N. d. 10N. 32 The space between the stars is not quite empty. It contains faint traces of gas as well as charged particles. If this interstellar medium were removed, the light from the stars a. would no longer reach us. b. would still reach us. c. would reach us only from stars emitting stellar winds.