Certain force acting on a 20 kg mass cha | Class 9 Science Chapter Work and Energy, Work and Energy NCERT Solutions

Question:

Certain force acting on a 20 kg mass changes its velocity from 5 m s-1 to 2 m s-1. Calculate the work done by the force.

Answer:

Mass of the body = 20 kg

Initial velocity, u = 5 m/s

Final velocity, v = 2 m/s

Kinetic energy is given by the expression,

(i) Kinetic energy when the object was moving with a velocity 5 m/s

(ii) Kinetic energy when the object was moving with a velocity 2 m/s

Work done = change in kinetic energy. 

Therefore, work done = (Ek)2 - (Ek)5

= 40 − 250 = −210 J

The negative sign indicates that the force is acting in the direction opposite to the motion of the object.


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Welcome to the NCERT Solutions for Class 9 Science - Chapter . This page offers a step-by-step solution to the specific question from Excercise 5 , Question 4: Certain force acting on a 20 kg mass changes its velocity from 5 m s-1 to 2 m s-1. Calculate th....