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MECHANICS UNIFORM ACCELERATED MOTION 1) The three toed sloth is the slowest moving land mammal on the ground, it moves with a velocity of 0.037 ms-1 , considerably slower than the giant tortoise which walks at 0.076 ms-1. If they both set off at the same time what is their separation after 12 mins of walking ? 2) A particle has a initial velocity of + 112 ms-1 at t = 0, it has no acceleration until t = 3s and from then on it has an acceleration of -4 ms-1. What is its velocity at t = 16s ? 3) The length of a barrel of a primitive blow gun is 1.2m. Upon leaving the barrel the dart has a speed of 14 ms-1. If the acceleration is constant how long does it take the dart to travel the length of the barrel ? 4) Suppose a car is travelling at 12 ms-1 and the driver sees a red light. After 0.510s (his reaction time) he depresses the brakes and the car decelerates at 6.2 ms-2. What is the total stopping distance of the car ? 5) A golf ball is dropped and rebounds off the ground with a velocity of 5 ms-1 to what height does the ball rise to ? 6) How long does it take until the between this bounce and the next ? 7) At what initial velocity must an arrow be fired straight up to attain a height of 110m in 5.4s ? IMPULSE & MOMENTUM 8) What is the impulse of a 35N force that acts on an object for 0.4s? 9) A woman drives a golf ball (mass = 0.045kg) with an initial velocity of 28 ms-1. The impact is of duration 6 * 10-3 s. a) What is the change in momentum ? b) What is the average force applied to the ball ? 10) A 55kg swimmer is standing on a stationary 210kg floating raft. The swimmer runs off the raft with a velocity of +4.6 ms-1, what is the recoil velocity of the raft ? 11) An astronaut is motionless in outer space and upon a command the propulsion unit on his back ejects some gas with a velocity of +14 ms-1. The astronaut (mass 160kg) recoils with a velocity of -0.5 ms-1. What was the mass of the gas ? 12) A two stage rocket moves in space with a constant velocity of 4900 ms-1. The two stages then are separated by a small explosion and the 1200kg upper stage moves off at 5700 ms-1 in the same direction. What is the velocity of the 2400kg lower stage after the explosion ? 13) In a game of American football a receiver is standing still, having just caught the ball, before he can move a tackler running at +4.5 ms-1 grabs him and the two move off together with a velocity of +2.6 ms-1. If the mass of the tackler is 115kg what is the mass of the receiver ? 14) In movies Superman hovers stationary in mid-air, grabs a villain by the throat and throws him backwards whilst he remains stationary. Using the law of conservation of linear momentum, explain what is wrong with this situation.