19. The kinetic energy of a car is 1.5×10, as it travels along a horizontal road

Question

19. The kinetic energy of a car is 1.5×10, as it travels along a horizontal road. How much power is required to stop the car in 20 see? a) zero watts b) 6.3 × 10" w c) 4.4× 106 w d) 2.4 x 10 w e) 7.5× 103 w 20. A 1200 kg car accelerates from rest to 28 m/s in a distance of 120 m. What is the magnitude of the average net force acting on the car? a) 3,920 N b) 470,400 N c) 33,600 N d) 144,000 N e) 16,800 N 21. A car is traveling at 5 m/'s when the driver applies the brakes. The car moves 2.5 m before it comes to a complete stop. If the car had been moving twice as fast, at 10 m/s, how far would it take to stop the car? Assume the braking force is the same in both cases. be) 2.5 m ac) 5.0 m ab) 12.5 m de) 10.0 m be) 7.5 m

Explanation / Answer

19]

Net work done = change in kinetic energy

W = [1/2]m[v2 - u2] = 150000 J

so, P = W/t = 150000/20 = 7500 Watt [option - e]

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