Question

The driver of a bus travelling at 72km/hr suddenly notices an elephant that completely blocked the road at a distance of 100m .what should be minimum deceleration that needs to be applied in order to prevent on accident. ​

Answer 1

Answer:

=72km/hr=

18

72×5

=20m/s

Time taken to cover the distance of 5m is:

t=

20

5

=0.25sec

This time is called Reaction time.

Answer 2

Answer:

Initial velocity(u) = 72 km/hr

= 72* 1000 m/ 3600 sec

= 20 m/s

Final velocity(v) = 0 m/s

Distance(S) = 100 m

Acceleration(a). = ?

Using the 3rd equation of motion,

v²= u²+2aS

(0)²=(20)²+ 2*a*100

=> 0 = 400+ 200a

=> -400= 200a

=> a = -400/200

=> a = -2 m/s²

Therefore acceleration(a)= -2 m/s²

or deceleration = 2 m/s²

Hope it helps :)