Question

31. A car travels with a uniform velocity of 25 m s-1 for 5 s. The brakes are then applied and the car comes to rest
with a uniform retardation in a further 10 s. Draw a velocity-time graph and use it to find
(a) distance which the car travels after the brakes are applied
(b) the retardation​

Answer 1

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