Question

A body of mass 15 kg moving with a velocity of 10 m/s has its velocity reduced to 6 m/s in two seconds. The force that produced this change in velocity is​

Answer 1

Given info : A body of mass 15 kg moving with a velocity of 10 m/s has its velocity reduced to 6 m/s in two seconds.

To find : The force that produced this change in velocity is ...

solution : initial velocity, u = 10 m/s

final velocity, v = 6 m/s

time taken to change the velocity, t = 2 sec

using formula, v = u + at

 ⇒ 6 m/s = 10 m/s + a × 2 sec

⇒ - 4m/s = a × 2 sec

⇒ a = - 2m/s²

From Newton's 2nd law of motion, F = ma

mass of body, m = 15 kg

acceleration , a = - 2 m/s²

∴ F = 15 kg × - 2m/s² = - 30 kgm/s² = -30N  [∵ 1kgm/s² = 1N ]

here negative sign indicates that the force applied on the body against its motion.

Therefore the force that produced this change in velocity is 30N.