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Learning Tweet Units of momentum (change in momentum) = kgm/s Change in momentum depends on the size of the force and the time it acts Change in momentum = resultant force (N) x time (s) Unscramble the words & make two sentences NCEDSTI EMIT ELVICYT HAGPR EPEDS CELECATNIOAR DISTANCE TIME VELOCITY GRAPH SPEED ACCELERATION Momentum answers 1 A– B C football = 12.5 kg m/s Tennis ball leaving racquet = 3kg m/s Golf ball = 2.05 kg m/s Car = 22000 kg m/s Lorry = 130 000 kg m/s Van = 77500 kg m/s sprinter = 500 kg m/s Dog = 120 kg m/s Cyclist = 910 kg m/s Momentum answers 2 1 a b c d 2 5000 kg m/s 31 600 kg m/s 720 000 kg m/s 480 000kg m/s 1.8 x1029 kg m/s 3 31.6 m/s (about 70 mph ) Momentum answers 3 1 A B 2 A B C 23000 kg m/s - 5400 kg m/s 9 kg m/s -9kg m/s 18 kg m/s Change in momentum Momentum = Mass x velocity Force x time (during which the force acts) = change in momentum Problems A snooker cue hits a ball. The ball has a mass of 0.17 kg and starts moving with a velocity of 1.4m/s. A What is the momentum of the ball Momentum = 0.17 x 1.4 = 0.238 kg m/s B The contact between the cue and the ball lasts for 0.1s. What is the average force exerted on the cue ball during this time? F x t = change in momentum F= change in mom/time = 0.238/0.1 = 2.38 N Problems (2) A motorcycle with a mass 200kg has a rider with a mass 50kg. It is travelling at 27 m/s (60 mph) a What is the momentum of motorcycle & rider b What braking force is needed to bring the motorcycle and rider to stop in 5s? Problems (3) A car (mass 1025kg) has collided with a brick wall. It was travelling at 23m/s(50mph) What was the momentum of the car The accident investigator estimated that it took 1.8s to stop. What average force was exerted on the car during the collision.