Question

A cyclist covers 15m/s and applies brake so that he doesn't clide to wall 18m ahead . find deacceleration and time..Please tell its urgent

Answer 1

Initial velocity,u=15 m/s
Final velocity,v = 0 kmh↑-1  
Distance,s = 18 m
v =u +2as
0=15 +2*18a
0=225+36a
-225/36=a
-6.25 m/s²

Answer 2

SUVAT-- s-displacement, u-initial velocity, v-final velocity,a- acceleration, t-timev=u + atv2 = u2 + 2ass=1/2(u+v)ts=ut + 1/2at2

His initial velocity, u is 15m/s
Her final velocity is, v 0m/s (since she stops)
Displacement is, s 18m
Hence the acceleration, a :

v2=u2 + 2as

0=15^2 + 2 x a x 18
0=225 + 36a
36a= -225

a =  -225/36
a= -6.25 m/s/s

Therefore she has to decelerate at the rate of 6.25m/s2

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