Question

If a truck is moving with velocity 40
km/hr applies brakes to save a child
at 25 m standing from the point from
where brake is applied. If the time
taken to stop the truck is 2 sec. Will
the truck kill the child?​

Answer 1

Hope it helps you to understand it easily.................

Explanation:

Here, V(Final velocity)=0 m/s(truck stops)

, U(initial velocity)=40Km/h

=40×5/18

=200/18

=100/9m/s

Time(t)=2 seconds

Acceleration(a)=(V-U)/t

=(0-100/9)/2

= -100/9×1/2

= -100/18

= -50/9m/s^2

according to the equations of motion,

=> S=ut+1/2at^2

Here,S=Distance travelled

=> S=100/9×2+1/2×(-50/9)×2^2

=> S=200/9+1/2×(-50/9)×4

=> S=200/9+(-25/9)×4

=> S=200/9+(-100/9)

=> S=200/9+(-100/9)

=> S=100/9

=> S=11.11metres

Hence,as the truck will only travel 11.11 metres the truck will not kill the child .