Chapter 7 Energy and Machines Unit Test - Ms. Nechita

Transcription

1 hapter 7 Energy and Machines Unit Test - Ms. Nechita Your Name: Printed Feb 26, :12 PM Question #1 of 38 1 pt - Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr? ) the 60 km/hr car ) the 30 km/hr car ) oth have the same kinetic energy. ) More information is needed about the distance traveled. Question #2 of 38 1 pt - When an automobile is braked to a stop, its kinetic energy is transformed to ) stopping energy. ) heat. ) energy of motion. ) potential energy.

2 E) energy of rest. E Question #3 of 38 1 pt - What is being explained by this image? a) forces are equal on both sides of the lever. b) distances are equal on both sides of the lever. c) the left side of the lever will need a larger downward force to lift the load on the right. d) the left side of the lever will move through a greater distance to lift a larger load on the right.

3 Question #4 of 38 1 pt - TV set is pushed a distance of 2 m with a force of 20 N. How much work is done on the set? ) 40 J ) 800 J ) 2 J ) 10 J E) 20 J E Question #5 of 38 1 pt - n object lifted 10 meters gains 200 J of potential energy. If the same object is lifted 20 meters, its potential energy gain is ) the same. ) four times as much. ) half as much.

4 ) twice as much. E) more than four times as much. E Question #6 of 38 1 pt - 2 kg mass has 40 J of potential energy with respect to the ground. pproximately how high is it above the ground? ) 1 m ) 2 m ) 4 m ) 3 m E) none of these E

5 Question #7 of 38 1 pt - If a charging elephant has kinetic energy, it must also have a. potential energy. b. momentum. c. acceleration d. ll of these. Question #8 of 38 1 pt - The power required to exert 1 N force, over a distance of 1 m in 1 second is ) 3 W. ) 1 W. ) 1/3 W. ) 2 W. E) none of these E

6 Question #9 of 38 1 pt - car moves 4 times as fast as another identical car. ompared to the slower car, the faster car has ) 8 times the KE. ) 16 times the KE. ) 12 times the KE. ) 4 times the KE. Question #10 of 38 1 pt - Neglecting friction, which will have the greatest kinetic energy when it just reaches the ground? a) a b) b

7 c) c d) all the same Question #11 of 38 1 pt - How much work is done on a 200-kg crate that is hoisted 2 m in a time of 4 s? (on't forget a mass is not a force) a. 400 J b J c J d J Question #12 of 38 1 pt - bow is drawn so that it has 40 J of elastic potential energy. When fired, the arrow will ideally have a kinetic energy that is ) more than 40 J. ) 40 J.

8 ) less than 40 J. ) impossible to predict without additional information Question #13 of 38 1 pt - In an ideal pulley system, a woman lifts an 80-N crate by pulling a rope downward with a force of 20 N. For every 1-meter length of rope she pulls downward, the crate rises a. 50 cm. b. 45 cm. c. 25 cm. d. less than 25 cm. Question #14 of 38 1 pt -

9 What holds the coaster cars in place? a) gravity b) inertia c) centripital force d) seat belts Question #15 of 38 1 pt - If Mr. Hewitt drops the bowling ball pendulum and stands very still, will it come back and hit him in the face?

10 a) Yes, because it can move highter than the release height due to its inertia. b) No, it cannot gain total energy. c) Yes, because potential energy turns to kinetic energy. d) No, because it has too much gravity. Question #16 of 38 1 pt - Rank the following points by largest kinetic energy to smallest E Question #17 of 38 1 pt -

11 n object that has kinetic energy must be ) at rest. ) at an elevated position. ) moving. ) falling. E) none of these E Question #18 of 38 1 pt - job is done slowly, while an identical job is done quickly. oth jobs require the same amount of work, but different amounts of ) energy. ) effort. ) power. ) none of these

12 Question #19 of 38 1 pt - diver who weighs 500 N steps off a diving board that is 10 m above the water. The diver hits the water with kinetic energy of ) more than 5000 J. ) 510 J. ) 5000 J. ) 500 J. E) 10 J. E Question #20 of 38 1 pt - The most energy per unit mass can be extracted from a. coal. b. petroleum. c. natural gas. d. uranium.

13 Question #21 of 38 1 pt - Which of these forms of energy is NOT renewable? a. wind power b. solar power c. fossil-fuel power d. photovoltaic power Question #22 of 38 1 pt -

14 If the distance the hand pulled the string is.4m or 40cm. What is the distance the load will have been lifted? a).8m b).2m c) 1.2m d).4m Question #23 of 38 1 pt -

15 If you push an object twice as far while applying the same force, you do ) twice as much work. ) half as much work. ) the same amount of work. ) four times as much work. Question #24 of 38 1 pt - Fill in the missing numbers for PE and KE

16 a) 10,000, 0 b) 7500, 5000 c) 7500, 2500 d) 2500, 7500 Question #25 of 38 1 pt - How much power is required to raise a 200-kg crate a vertical distance of 2 m in a time of 4 s? a. 400 W b W c W d W Question #26 of 38 1 pt -

17 What task requires the most work; lifting a 50-kg sack 2 meters or lifting a 25-kg sack 4 meters? ) the 25-kg sack ) the 50-kg sack ) oth require the same amount of work. ) impossible to determine without knowing the contents of the sack Question #27 of 38 1 pt - 1) If you push for a half hour or a whole hour against a stationary wall ) no work on the wall is done in either case. ) twice as much work is done during the half hour. ) half as much work is done during the half hour. ) it is impossible to determine how much work is done.

18 Question #28 of 38 1 pt - The ball rolling down an incline has its maximum potential energy at ) the bottom. ) the top. ) halfway down. ) a quarter of the way down. Question #29 of 38 1 pt - When work is done twice as quickly, then the power expended is a. half. b. the same. c. twice. d. 4 times as much. Question #30 of 38 1 pt -

19 clerk can lift containers a vertical distance of 1 meter or can roll them up a 2 meterlong ramp to the same elevation. With the ramp, the applied force required is about ) the same. ) four times as much. ) half as much. ) twice as much. Question #31 of 38 1 pt - pendulum bob swings to and fro. Its kinetic energy and its potential energy relative to the bottom of its swing are the same at a. the bottom. b. one-quarter the vertical distance between the bottom and top of the swing. c. one-half the vertical distance between the bottom and the top of the swing. d. the top of the swing. Question #32 of 38 1 pt -

20 If the man's input force is 100N, what is the mechanical advantage? a) 1 b) 4 c) 5 d) 6 Question #33 of 38 1 pt - o 100 J of work in 50 s and your power output is ) 1/2 W ) 2 W.

21 ) 5,000 W. ) 4 W. E) 50 W E Question #34 of 38 1 pt - feather and a coin dropped in a vacuum fall with equal ) accelerations. ) kinetic energies. ) forces. ) momenta. E) none of these E

22 Question #35 of 38 1 pt - When you do 1000 J of work on a car jack and the gravitational potential energy of the car is increased by 300 J, the efficiency of the jack is a. 30%. b. 50%. c. 70%. d. 130%. Question #36 of 38 1 pt - If an object has kinetic energy, then it also must have ) force. ) momentum. ) acceleration. ) impulse. E) none of these E

23 Question #37 of 38 1 pt - n object may have potential energy because of its ) momentum. ) acceleration. ) speed. ) location. E) none of these E Question #38 of 38 1 pt - fter rolling halfway down an incline, a marble's kinetic energy is ) greater than its potential energy. ) the same as its potential energy. ) less than its potential energy. ) impossible to determine.

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