Question

find the initial velocity of the car which is stopped in 10 second by applying brakes the retardation due to break is 2.5 M per second square

Answer 1

here t=10 sec
a= -2.5m/s²
v=0
thus by equation of motion v=u+at
u=v-at
u=-(-2.5*10)
thus u=25 m/s
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Answer 2

The required formula is v = u - at

where, v = final velocity ; u = initial velocity ; a = retardation ; t = time.

Given; v = 0 m/s

t = 10 sec

a = 2.5 m/s²

Putting the values in formula mentioned above,

0 = u - (2.5 x 10)

or, u = 25

Thus the initial velocity of the car was 25 m/s.