1. CHAPTER 4 SECTIONS 1 & 2 Work, Power and Machines

2. 1. What is work? A. The type of energy that a moving object has B. The rate at which work is done or energy is transformed C. The unit used to express power D. The transfer of energy using a force that causes an object to move in the direction of the force

3. ANSWER: Work is… D. The transfer of energy using a force that causes an object to move in the direction of the force

4. 2. What is power? A. The type of energy that a moving object has B. The rate at which work is done or energy is transformed C. The unit used to express power D. The transfer of energy using a force that causes an object to move in the direction of the force

5. ANSWER Power is… B. The rate at which work is done or energy is transformed

6. 3. What is kinetic energy? A. The type of energy that a moving object has B. The rate at which work is done or energy is transformed C. The unit used to express power D. The transfer of energy using a force that causes an object to move in the direction of the force

7. ANSWER Kinetic energy is … A. The type of energy that a moving object has

8. 4. What is a machine? A. The type of energy that a moving object has B. The rate at which work is done or energy is transformed C. A device that helps do work by either overcoming a force or changing the direction of the force D. The transfer of energy using a force that causes an object to move in the direction of the force

9. ANSWER A machine is… C. A device that helps do work by either overcoming a force or changing the direction of the force

10. 5. What is work input? A. A number that tells how many times a machine multiplies a force B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input C. The work done ON a machine D. The work done BY a machine

11. ANSWER Work input is… C. The work done ON a machine

12. 6. What is work output? A. A number that tells how many times a machine multiplies a force B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input C. The work done ON a machine D. The work done BY a machine

13. ANSWER Work output is… D. The work done BY a machine

14. 7. What is mechanical advantage? A. A number that tells how many times a machine multiplies a force B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input C. The work done ON a machine D. The work done BY a machine

15. ANSWER Mechanical advantage is… A. A number that tells how many times a machine multiplies a force

16. 8. What is mechanical efficiency? A. A number that tells how many times a machine multiplies a force B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input C. The work done ON a machine D. The work done BY a machine

17. ANSWER Mechanical efficiency is… B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input

18. 9. In which situation is a person doing work on an object? A.A school crossing guard raises a stop sign that weighs 10 N. B.A student walks while wearing a backpack that weighs 15 N. C.A man exerts 350 N force on a rope attached to a house. D.A worker holds a box 1 m off the floor.

19. ANSWER A.A school crossing guard raises a stop sign that weighs 10 N.

20. 10. Scott applies a force of 100 N to move a box 5 meters. How much work did he do? A.100 J B.500 J C.5 J D.500 N

21. ANSWER B.500 J

22. 11. If a barbell weighs 160 N, what other information do you need to calculate how much work it takes to lift it? A.The shape of the weights B.The height the barbell is being lifted C.The strength of the person doing the lifting D.The amount of output force

23. ANSWER B.The height the barbell is being lifted

24. 12. Tom used 75 N of force to push a box 3 m across the floor. How much work did he do? a. 25 J b. 25 N c. 225 J d. 225 W

25. ANSWER 75 N x 3 m = c. 225 J

26. 13. Which of the following prevents machines from being 100% efficient? a. friction b. input force c. output force d. power

27. ANSWER a. friction

28. GOOD LUCK ON TUESDAY!! STUDY HARD!! A copy of this guide is available on our websites: Frost.sd54.org/mrcscience and Frost.sd54.org/dzuffante