Question

3. A car travelling at 60.0 m/s forward slows down to 40 m/s forward in 2.5 seconds. Assuming that this acceleration continues, how many seconds would it take the car to slow to (a) 20 m/s forward? (b) rest? 4. A toy car is propelled forward from rest by a girl's hand reaching a velocity of 6 m/s in 0.40 seconds. It is then released and stops in 2 seconds. (a) With what acceleration did the car speed up (a AvAt)? (b) What is the average speed in the 1s 0.40 seconds? (c) With what acceleration did the car slow down? (d) What is the average speed from 0.4 to 2.4 s? (e) Plot a velocity vs time graph of its motion

Answer 1

3.

Given v_i = 60 m/s v_f = 40 m/s t = 2.55 Here acceleration will be a = v_f - v_i/t = 40 - 60/2.5 m/s/s v_f = 12 m/s t = ? a = -8m/s^2 t = v_f - v_i/a = 12 - 40 m/s/-8 m/s^2 = 3.55 from the time when v_i = 40 m/s v_f = 0.0 m/s t = ? t = v_f - v_i/a = 0.0 - 40 m/s /-8 m/s^2 = 5.05 from the time when v_i = 40 m/s

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