Question

A car is travelling with a speed of 72 km/hr. If the car comes at rest after 5 seconds when brakes are applied, what is the retardation?

Answer 1

To find the retardation (deceleration) of the car, we can use the formula:

retardation = (final velocity - initial velocity) / time

Given: Initial velocity (u) = 72 km/hr Final velocity (v) = 0 km/hr (since the car comes to rest) Time (t) = 5 seconds

First, let's convert the initial velocity from km/hr to m/s to ensure consistent units:

Initial velocity (u) = 72 km/hr = (72 * 1000) m/3600 s = 20 m/s

Now, we can calculate the retardation using the formula:

retardation = (0 - 20) m/s / 5 s = -20 m/s / 5 s = -4 m/s²

Therefore, the retardation of the car is -4 m/s² (negative sign indicates deceleration).