Question

21). A car moving along a straight road with a
speed of 120 km/hr, is brought to rest by
applying brakes. The car covers a distance
of 100 m before it stops. Calculate (i) the
average retardation of the car (ii) time
taken by the car to come to rest.
[Ans: 50/9 m/sec, 6 sec]​

Answer 1

Answer:

(1)

u = 120

v = 0

s = 100

a = ?

v² = u² - 2as

0 = (120)² - 200a

200a = 120 * 120

a = 120 * 120/200

a = 72 ms-²

(2)

Time taken by car to come at rest =

v = u + at

0 = 120 - 72t

72t = 120

t = 120/72

5/3