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UNL2207 - The Nature of Natural Law: Tutorial 5 Conservation Laws 1) A roller coaster is pulled to the top of a chute and allowed to roll down (ignore friction), arriving at the bottom at a certain speed. height To get a bigger thrill and arrive at the bottom with twice this speed, the chute would need to be a) twice b) three times c) four times d) five times e) six times as high. 2) Suppose an open railroad car is rolling without friction in a vertically- falling downpour and an appreciable amount of rain falls into the car and accumulates there. Consider the effect of the accumulating rain on the speed, momentum and kinetic energy of the car. Each of these will respectively a) increase 3) b) decrease c) not change Explore the physics simulation http://www.walter-fendt.de/ph14e/ncradle.htm Write down the equations expressing conservation of momentum and conservation of energy for these two systems respectively and use your equations to discuss the observed motions. 1 4) A rubber bullet and an aluminum bullet both have the same size, speed and mass. They are fired at a block of wood. Which is most likely to knock the block over? Which is most likely to damage the block? 5) A ball attached to a string is rotating in a large horizontal circle. The string is then pulled in so that the ball now rotates in a smaller circle. When the ball is spinning around the smaller circle, it’s speed is a) greater b) less c) unchanged 6) Pull a pendulum to one side and let it go; as it swings back and forth, the pendulum is conserving a) linear and angular momentum b) only angular momentum c) only linear momentum d) neither linear nor angular momentum 7) A geosynchronous satellite is one that stays above the same point on the equator of the Earth. Such satellites are used for such purposes as TV transmission, for weather forecasting, and as communications relays. Determine a) the height above the Earth’s surface such a satellite must orbit and b) such a satellite’s speed. c) With what velocity (speed and direction) would the satellite have to be launched if it is to escape from the earth’s gravitational field altogether? 2