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Exam 2 practice problems

Exam 2 practice problems - Exam#2 practice problems Physics...

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Exam #2 practice problems Physics 203 1. You are trying to find a short cut across a calm river ( 20.0 m wide) without getting wet. Someone left their kayak on the bank but the paddle is nowhere to be found. So, you put the kayak in the water pointed at the opposite bank of the river. You then get a running start and jump onto the kayak. You and the kayak glide at a nearly constant rate until you reach the opposite side. However, you were having so much fun doing all this that you lost track of time as you were crossing the river. You realize, thanks to taking physics over the summer at Rutgers, that you can actually predict how long it took to cross the river. You estimate that you have a mass of 70.0 kg , the kayak has a mass of 20.0 kg , and that you were running at about 3.00 m s when you jumped onto the kayak. Predict how long it took to cross the river. 2. You are playing pool and need to hit a very specific shot. You need the cue ball (mass 0.17 kg ) to hit the 3-ball (mass 0.16 kg ) so that the following happens: 1) After it hits the 3-ball the cue ball needs to be traveling very slowly (you guess 0.1 m s ) at a 90 degree angle counterclockwise from its original direction of travel so it stops at a specific place on the table. 2) The 3-ball needs to be traveling at a 20 degree angle clockwise from the cue ball’s original direction of travel. What speed must you give the cue ball in order to pull off this shot? 3. You are ice skating on a frozen lake and headed towards your friend at 2.00 m s . You hold your arm out to the side, and your friend digs into the ice with his skates so he won’t move. Your friend grabs your outstretched arm as you are passing him causing you to turn rapidly around him. He releases your arm at just the right time so you end up heading directly back in the direction you came from traveling at the same speed. a. Draw a motion diagram for you during this situation. b. Predict the force that your friend had to exert on you. If you have to estimate any additional physical quantities feel free to do so, but make sure you make reasonable estimates. 4. A new idea for an amusement park ride came up in the 1950’s called “The Rotor”. People would stand with their backs to the wall in a circular room, then the entire room would start rotating. The people felt themselves being pressed into the wall harder and harder. Then, the floor would drop out! Rather than fall, they would remain stuck to the wall. a. Use your understanding of forces and motion to explain why the people felt as they did. Explain how it is possible that the people could remain stuck to the wall. Use a free body diagram to illustrate your explanation. b. Some riders on early models of “The Rotor” expressed discomfort after being on the ride for more than a minute. In order to reduce this discomfort the fairly smooth wooden walls were replaced with wooden walls that were rougher. This allowed the ride to spin more slowly. Predict the coefficient of static friction needed so that the
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