Question

A motorist is travelling at 72 kmph along a straight road. A traffic signal turns red and it remains red for 15 s. What must be deceleration so that at signal the velocity is zero

Answer 1

u=72km/hr or 72×5/18= 20m/s

t=15sec

v=0

Apply laws of motion,

v=u+at

0=20+15a

a= -20/15

a= -4/3 or -1.33m/s^2

Deceleration= 1.33m/s^2 (Deceleration

itself

means -ve)