Question

9. A bus of mass 1500 kg decreases
its speed from 90 km/h to 72 km/h in
5 s. Find the value of friction force
which is applied by brakes.
O 2000 N
0 1500 N
O 4500 N
0 700 N​

Answer 1

Explanation:

When a object is moving with a constant velocity, it possess K.E

K.E= 21×m×v 2

So, in order to bring the object to rest i.e its same magnitude of energy is required so, as the final final energy comes to zero.

v=60km/hr=16.66m/s

So, magnitude of work that needs to be done = 21 ×m×v 2

Hence, work required to stop the car = 21×1500×16.66 2

=208166.7J=208.17kJ