Question

A car moving at 20ms-1 starts to slow down at 4ms-2 when it comes to a junction. The distance the car will travel before it comes to a stop will be ?

Answer 1

use 1st equation of motion
Vf=Vi+at
put Vf=0 b/c the car finally come to rest.
u'll get time t=5 sec
now use 2nd equation of motion i.e;
S=Vi(t)+1/2a(t)^2
put the values:
Vi=20m/s
t=5sec
u'll get S=150m