A car weighing 9800N is moving with a speed of 40km/h. on the application of the brakes it comes to rest after traveling a distance of 50metres .Calculate the average retarding force.
Answers
Answer:
1209.63N
Explanation:
Conservation of energy allows you to work out the decelerating force. It is assumed that no other forces - like mechanical friction in the car’s bearings or air resistance - are involved to complicate matters.
Parameters involved are …
s - the braking distance to bring the car to rest
u - the initial speed at the time braking starts
v - the fnal speed which of course is zero
m - the mass of the vehicle
m = 9800 / 10 kg (where the acceleration due to gravity is taken as 10 ms^-2).
So, m = 980 kg.
The initial speed, u, is 40 kmh^-1 which is 11.11 ms^-1
The dissipation of the car’s kinetic energy in the brakes over the braking distance to rest can then be calculated using,
Kinetic energy, Ek = work done by the braking force
[(1/2) * m * u^2] - [(1/2) * m * v^2] = F x s
(1/2 * 980 * 11.11^2 = F * 50
so F = 1209.63 N