Physics 115 Test 2A with key


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Unformatted text preview: direction: toward shooter) The vector sum of these two momenta is the total momentum after the sh ot, but this mus t equal the total momentum before the shot (conservation of momentum), which was zero. If we take the plus sign (+) to indicate the direction away from the shooter , and the minus sign (–) to indicate the direction toward the shooter, we get 3.5 3.5 7 vrifle 0 3.5 7vrifle vrifle 0.5 m/s 7 Question 4 – As you swing back and forth on a playground sw ing, your apparent weight changes. At which point do you feel the heaviest? a. b. c. d. at the lowest point of your swing at the top of your swing going either forward or back ward at the top of your swing going backward in the middle of your swing going forward, but not ye t at the lowest point Answer (a) You move back and forth along part of a circle (a so‐called arc). The centripetal force is biggest at the lowest point of your swing, because that’s where you go fastest. Here, like it does all the t ime when you’re swinging, the centripetal force points along the chains of the swing to its pivoting points. So there the fee ling of acceleration points away in the same direction, and, like we said, is biggest at the bottom of your swing. You mu st now add the gravitational weight m x g, and you that your apparent weight is biggest at the lowest point. Question 5 – T he cart is pulled to...
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