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## Homework Statement

Some of these questions are easy and I just want to make sure i"m right. Others are pretty hard for me. Please only do a few problems because there are a lot and i don't want to overload anyone. If several people could help me by each doing a few problems it wouldn't be a hassle for you guys and would be a huge help for me. Thanks in advance. You can show me how you got the answer if you would like, but again there are a lot of problems so if you don't have time dont worry about showing the work. Thanks.

1. A 1000 kilogram sports car accelerates from rest to 25.0 m/s in 7.5 seconds. What is the average power output of the automobile engine. Choices: A. 20.8 KW, B. 30 KW, C. 41 KW, or D. 52.4 KW I believe the answer is C but I'm not sure.

2.The more powerful the motor is A. The longer the time interval for doing the work is. B. the shorter the time interval for doing the work is. C. the greater the ability to do work is. or D. the shorter the workload is. I believe the answer is C to this, but again not 100% sure.

3. A hill is 100 meters long and makes an angle of 12 degrees with the horizontal. As a 50 kilogram jogger runs up the hill how much work does gravity do on the jogger? A. 50,000 J, B. 10,000 J, C. -10,000 J, or D. 0 J I believe the answer is a.

4. A flight attendant pulls a 50.0 N flight bad a distance of 250 meters along a level airport floor at a constant speed. A 30 N force is exerted on the bag at an angle of 50 degrees above the horizontal. How much work is done on the flight bag? A. 12500 J, B. 7510J, C. 4821 J, D 8040 J. I believe it is C.

5. Which of the following energy forms is involved in winding a pocket watch. A. electical energy, b. nonmechanical energy, c. gravitational potential energy, or d. elastic potential energy. I think it is d.

6. which of the following energy forms is involved in a pencil falling from a desk. a. kinetic energy. b. nonmechanical energy, c. gravitational energy, or d. elastic potential energy and kinetic energy. I think it is A. but im not sure.

7. If the only force acting on an object is friction during a given physical process, which of the following assumptions must be made with regard to the objects kinetic energy?

A. the kinetic energy decreases, B. the kinetic energy increases. C. the kinetic energy remainds constant, or D. the kinetic enery decreases and then increases. I think it is A.

8. WHich of the following energy forms is associated with an object in motion. A. potential energy, B. elastic potential energy. C. nonmechanical energy, or D. kinetic energy. I think it is D.

9. which of the folowwing parameters does not express how resistant a spring is to being compressed or stretched? a. compression distance, b. relaxed length, c. spring constant, or d. stretching distance?

10. A 16 KG child on roller skates initially at rest rolls 2.0 m down an incline at an angle of 20 degrees with the horizontal. If ther eis no friction between incline and skates what is the kinetic energy of the child at the bottom of the incline? A. 210 J. B> 610 J. C. 11 J. D. 107 J

11.. A pole vaulter clears 6 meters. With what velocity does the vaulter strike the mat in the landing area? (I think this is assuming the vaulter clears exactly 6 meters and no higher). A> 2.7 M/s B. 5.4 M/s C. 45 M/s D. 54 M/s.

12.A bobsled zips down an ice track starting at 150 m vertical distance up the hill. Disregarding friction, what is the velocity of the bobsled at the bottom of the hill?

13. A 40 N crate starting at rest slides down a rough 6 meter long ramp inclined at 30 degrees with the horizontal. The force of friction between the crate and the ramp is 6 Newtons Using the work-kinetic energy theorem find the velocity of the crate at the bottom of the incline. A. 8.7 m/s b. 3.3 m/s c. 45 m/s d 54 m/s

14. A parachutist with a mass of 50 kg jumps out of an airplane at an altiude of 1000 meters. After the parachute deploys the parachutist lands with a velocity of 5 meters per second. Using the work-kinetic energy theorem, find the energy that was lost to air resistance during the jump. A> 49300 J. B. 98800 J. C. 198000 J. D> 489000 J.

15. A child riding a vicyle has a total mass of 40 kg. the child approaches the top of a hill that is 10 meters high and 100 meters long. at 5 meters per second. if the force of friction between the bicycle and the hill is 20 newtons, what is the child's velocity at the bottom of the hill (disregard air resistance). A. 5 m/s B. 10 m/s. C. 11 m/s D. the child stops before reaching the bottom.

16. Water flows over a section of niagra falls at a rate of 1.2 x 10^6 kg/s and falls 50 meters. What is the power of the waterfall? (mega = 10^6). A> 590 MW. B. 294 MW. C. 147 MW. D. 60 MW

17. Explain how energy, time, and power are related.

18. a tired squirrel with a mass of 1 kg does pushups by applying a force to elevate its center of mass by 5 cm determine the number of pushups which a tired squirrel must do in order to do a mere 1 joule of work. If the tired squirrel does all this work in 4 seconds then determine its power.

## Homework Equations

I would give you them, but if I knew them I wouldn't be asking for help. :(

## The Attempt at a Solution

I put my attempts in the questions.