Question

A car of mass 1000 kg moving with a velocity of 20 m/s is brought to rest by applying brakes in 10 seconds. What is the force applied by the brakes?

• A. 1000 N
• B. 2000 N
• C. 4000 N
• D. 10000 N

Answer 1

The correct option is B 2000 N

In this case, m = 1000 kg, u = 20 m/s, v = 0, t = 10 s

Let the acceleration be ‘a’ and the force applied be ‘F’.
We know,
a = (v - u)/t
a = (0 - 20)/10 = -2 $m/s^2$

Since, F = m x a
⇒ 1000 x (-2) = -2000 N

(The negative sign indicates that the force is acting in a direction opposite to the direction of motion of the object.)
Therefore, the force applied by the brakes is 2000 N.