Question

A car travels with a uniform velocity of 20 m/s for 5s. The brakes are then applied and the car is uniformly retarded. It comes to rest in a further 8 s. Draw a graph of velocity against time. Use this graph to find
a. the distance traveled in the first 5 seconds.
b.The distance travel after the brakes are applied
c. Total distance traveled
d. acceleration during the first 5s and last 8s

Answer 1

Answer:

Retardation is obtained using the formula "v = u - a×t " , where v is final speed which is zero in this case,

u is initial speed , a is retardation and t is time

(1) retardation a = u/t = 25/10 = 2.5 m/s2 .

(2) distance travelled before applying break = 25×5 = 125 m

(3) distance S travelled after applying break is given by, S = u×t - (1/2)×a×t2 = 25×10 - (1/2)×2.5×100 = 125 m