Question

A body of mass 10 kg is moving with a velocity of 30 m/s. When brakes are applied, it stops after travelling a distance of 15 metres. Find retardation and retarding force

Answer 1

Answer:

30 m/s²    ;   300N

Explanation:

Using the equations of motions:

  v² = u² + 2aS

In the given question:  final velocity is 0(when the body stops), S is 15 m.

⇒ 0 = (30)² + 2a(15)

⇒ - 900 = 30a

⇒ - 30 = a

   Since, a(acceleration) is negative, it is retardation.

Retardation = - a = -(-30) = 30 m/s²

Retarding force = mass x retardation

                     = 10 kg x 30 m/s²

                     = 300 N

Answer 2

Given :-

Mass of body = 10 kg

Initial Velocity = 30 m/s

Final velocity = 0 m/s

To Find :-

Acceleration

Retarding force

Solution :-

$\sf v^{2} - u^{2} = 2as$

$\sf 0^{2} - 30^{2} = 2(a)(15)$

$\sf 0 - 900 = 30a$

$\sf -900 = 30a$

$\sf a = \dfrac{-9000}{30}$

$\sf a = 30 \; {m/s}^{2}$

$\bf F = ma$

$\sf F = -30 \times 10$

$\sf F = 300 N$