1. Review for Energy Exam

2. What is the work required for 60 kg astronaut to lift herself 0.2 m on Earth 0.2 m Ans. 120 J

3. What is the work required for a 60 kg astronaut to lift herself 0.2 m on Planet X? (g = 2 m/s 2 ) 0.2 m Ans. 24 J

4. What is the PE g of a 20,000 kg lunar lander that is 100 m above the surface of the Moon? (g = 2 m/s 2 ) 100 m Ans. 4,000,000 J

5. What is the KE at point C? h ½ h PE = 0 PE KE 20 J A B C D Ans. 10 J

6. What is the speed of the 1 kg ball at point C? h ½ h PE = 0 PE KE 20 J A B C D Ans. 4.5 m/s

7. The car at B has _____ times as much KE as it had at A 20 m/s40 m/s60 m/s ABC Ans. 4

8. The car at C has _____ as much KE as it had at A 20 m/s40 m/s60 m/s ABC Ans. 9

9. What is the primary form of energy present in this situation? Ans. PE s

10. What form(s) of energy are present in this situation? Ans. PE s, PE g

11. What was the work done on the 1000 kg car? 5 m/s25 m/s BeforeAfter Ans. 300,000 J

12. A 5 kg lead ball and a 2 kg wooden ball are dropped from the same height. Which has more PE g ? Ans. Lead ball

13. A 5 kg lead ball and a 2 kg wooden ball are dropped from the same height. How do their KEs compare before striking the ground? Ignore air resistance. Ans. Lead KE is greater

14. A 5 kg lead ball and a 2 kg wooden ball are dropped from the same height. How do their speeds compare before striking the ground? Ignore air resistance. Ans. Speeds same

15. The motion of a 2 kg cart is shown below. What is its KE at t = 6 s? 0 30 60 012345678910101 1212 1313 1414 1515 1616 1717 1818 1919 2020 Time (sec) Velocity (m/s) Ans. 900 J

16. If Sally and Sam have the same mass, which one has the greater KE? 0 0 position time Sam Sally Ans. Sally

17. What forms of energy does the baseball have? Ans. KE, PE g

18. What is the stiffness (k) of this spring? 0 30 60 012345678910101 1212 1313 1414 1515 1616 1717 1818 1919 2020 Stretch (m) Force (N) Ans. 6 N/m

19. What is the PE s when the spring is stretched to 5 m? 0 30 60 012345678910101 1212 1313 1414 1515 1616 1717 1818 1919 2020 Stretch (m) Force (N) Ans. 75 J

20. If all of the PE chem of a typical doughnut could be used to do work, how high could a 50 kg person climb? PE chem = 1,000,000 J ? Ans. 2 km

21. A skier has a choice of the following two frictionless slopes. Along which slope will he end up with the greatest speed at the bottom? Slope A Slope B Ans. Same speed

22. A diver falling from 2h will have _____ as much KE hitting the water as a diver falling from h Ans. twice

23. A diver falling from 4h will have _____ as much speed hitting the water as a diver falling from h Ans. twice

24. A 20 kg kid starts from rest at point A. What is his PE g at A? 6 m 3 m A B C Ans. 1200 J

25. What is the 20 kg kid’s PE g at point C? 6 m 3 m A B C Ans. 600 J

26. What is the 20 kg kid’s KE at point B? 6 m 3 m A B C Ans. 1200 J

27. What is the 20 kg kid’s KE at point C? 6 m 3 m A B C Ans. 600 J

28. What is the 20 kg kid’s speed at point B? 6 m 3 m A B C Ans. 11 m/s

29. What is the work done on the dog? Into what form of energy does this work go? Dog slides 2 m 30 N Dog is motionless at end Ans. 60 J; thermal

30. After hitting a 0.4 kg soccer ball with her head, it travels 6 m straight up. What was the work she did on the ball? 6 m Ans. 24 J