We are starting electrical circuits. Please read pages 531-534 and write down a few important pieces of information. Then, on pages 545-546, do Reviewing Questions # 1, 3, 4, 5, 6, 7, 8, 10, and 11.
starting with #16
a = F/m = 400N / 100 kg = 4 m/s/s 17. F net is the combination of all the forces. 600 N up cancels 600 N down. 35 N forward cancels 35 N backwards. Net force = 0. (there is a problem--where does the forward push of 35 N come from?) 18. Force down = 800 N from its weight. Force up is 900 N up. (and so the net force would be 100 N up) 19. If the block is NOT sliding down the slide, then the only force that could be pulling it back up the slide is friction. 20. If the velocity is constant, then the net force is zero. If you have to push it with 10 N just to keep in moving at a constant velocity, then something is pushing in the other direction. That something is friction. We call it kinetic friction because it is sliding across the surface. 10 N of kinetic friction. 21. The force of gravity depends on mass and how far the objects are from the center of the Earth. They have the same mass. Since their distance to the center of the Earth is about identical, the F gravity is also almost identical. 22. Reading the chart, the only one that is true is that she would weight more than twice as much on Jupiter. (by the way, this is because Jupiter has an enormous mass, many times greater than the Earth's mass). 23. We haven't studied these much. Thinking about Newton's first law (objects keep moving in straight lines) the correct answer is X. 24. In order to make something keep moving in a circle, you need to pull the object towards the center. Think about swinging keys on a string, or a whistle, or a yo yo. To get it to go in a circle, you have to pull it inward, in the direction of Z. 25. The club speeds up because of breakfast energy that the man is investing. He does work to the club, so it goes a lot faster at Y. The answer is D. 26. Total energy is KE + PE. It has 22.5 J of KE and 10 J of PE, for a total of 32.5 J. 27. An apple falling loses PE and gains KE. The other examples have an outside source of energy giving it more or less (whatever is lifting the crate gives energy to the crate, the car uses gasoline to gain KE, and the sky diver loses energy to the air. Also, GPE is short for Gravitational Potential Energy, what we call PE). 28. This is not a great question. The correct answer is D because each has gained 1/2 as much KE as they will have at the bottom. 29. W = Fd = 40 N X 0.2 m = 8 J. 30. If you lift it, it gains PE. The correct answer is C, because PE is a type of mechanical energy. 31. They both do the same amount of work. Since the second competitor does the work in less time, he generates more power. 32. The air conditioner uses the most, since it is on for an hour and would use 1000 Watts X 1 hour. 33. Momentum is conserved. The pair would slow down since the mass went up. 34. v = p / m = 25 m/s Open Response 1. Most of this is really really easy. Just read the parts and do a little bit of math. a. add b. speed = distance / time 1600 / 100 c. displacement is how far from where it started, and should include direction and units. d. average velocity is displacement / time. 800 / 100 2. a. Before it is pushed, it was pulled down by Earth and pushed up by table (F gravity and F normal) b. It started because you applied an outside unbalanced force, and gave it KE. Friction makes it stop. c. To make it go at a constant velocity, you would need to eliminate friction (impossible) OR keep on pushing it to balance out the force of friction. 3. a. KE = 1/2 m v v b. PE = mgh c. PE gets smaller as KE gets bigger d. Air resistance could have taken away some KE. due on MONDAY 4/14
Read and write down 4 important things from pages 508-514 On pages 515-516 Do Review Questions: 1, 2, 5, 6, 10, 17, 20a, 23 and 24 This may take you 30-40 minutes. Plan accordingly. |
AuthorMr. Gerard Gagnon Archives
May 2015
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