Documents you may need:
Extra practice: Ch. 10 & 11 Review sheet that was the worked on in class (pdf or google doc)
Energy Skate Park Lab (simulation is available here and free to download or run off their site) Lab writeup (pdf or google doc)
Physics Work Review of Labs (pdf or google doc)
Homework Help:
Rubric for CH 10 & 11 worksheet
pg. 287 #2, pg. 291 #6, 10, pg. 297 #18, pg. 307 #57
2. Remember W=(delta)E so if you find the change in energy, you will have found the work.(<6.4E5)
18. First find the amount of PE that the first diver has that steps off the platform. All of his PE becomes KE when he hits the water. The second diver would have to have more KE at the bottom than the first diver. Using the PEi=KEf of the first diver, find out what height the second diver would have to fall from in order to make that much PE. Notice that the second diver is smaller, what does that mean his height must be to have the same amount of PE?
6. The desk is h=0 so the difference between them is the height. (<30)
10. TWO calculations: First, the PE at 425 m (>1E5). And then in order to know the change from 425 m to 225 m you need to find the PE at 225 m. The difference between them is the change in PE. (<5E4)
57. a. (>2000) b. His new KE will not be half as much! c. Ratio = (a):(b)
pg. 272 #25, 26; pg. 273 #30; pg. 280 #81, 82
25. a. the effort distance is the distance the wedge is driven down (0.2) and the resistance distance is how far the log is split (0.05). (4)
b. The force needed to split the log is the resistance distance, the force exerted by the sledge hammer is the effort distance. (<4)
c. Use the efficiency equation with MA and IMA since you already have it. (<40%)
26. a. You are given the effort force but have to calculate the resistance force. Since you know the mass of the crate you can find its force of gravity; the resistance force is equal but opposite to the force of gravity. (<2)
b. Solve for the IMA first. The effort distance is how far the rope has to be pulled and the resistance distance is how far the crate actually moves. (2) Then use the efficiency equation with MA and IMA since you already have it. (>90%)
30. The worker can only exert an effort force of 875 N. We know that the effort distance is how far the worker moves the rope and the resistance distance is how far the rope moves. YOU HAVE TO ASSUME THAT IT IS 100% EFFICIENT IN ORDER TO SOLVE THIS PROBLEM. Set the Work in (Fede) equal to the work out (Frdr) and solve for the resistance force. (>5000)
81. Try this one on your own: a. (4), b. (<4), c. (<90)
82. a. You are given the effort force but have to calculate the resistance force. Since you know the mass you can find its force of gravity; the resistance force is equal but opposite to the force of gravity. (<4) b. (4), c. (<90)
pg. 261 #3, pg. 264 #10, 13, pg. 265 #17-20, pg. 278 #63
3. Sometimes the Force that is applied is against the Force of Gravity. You may need to find an object's weight (Force of Gravity) and assuming its being raised at a constant velocity you know the applied force is equal but opposite to that weight. So for some of your problems: W=Fd=-Fgd=-mgd a. (>600), b. (<6000), c. (>3)
10. a. Since W=Fd and P=W/t, you can substitute and get P=Fd/t or calculate them individually. b. Think of your practice problem today.
13. Since W=Fd and P=W/t, you can substitute and get P=Fd/t or calculate them individually. (>300 s)
18. Similar to #3. (<35,000)
19. Similar to #19 (<4)
20. Use W=Fd to find the Force applied. If lifted at a constant velocity the Force applied would be equal in magnitude but opposite in direction to the Force of Gravity. Use that information to find the mass of the box. (<600)
63. Apply what you did before in #3 and #10. (>2000)