Question

A cyclist is traveling at 15ms-1 she applies brakes so that she does not collide with a wall 18m away. what deceleration must she have?​

Answer 1

Answer:

In this question we will calculate the negative acceleration/deceleration, as follows:

Kinematic equations:

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

Her 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