Chapter 10

NCERT
Class 9
Science
Solutions
4. Certain force acting on a 20 kg mass changes it's velocity from 5 ms–1 to 2 ms–1. Calculate the work done by the force.

Question:

Certain force acting on a 20 kg mass changes it's velocity from 5 ms–1 to 2 ms–1. Calculate the work done by the force.

Answer:

Mass of the object m = 20 kg

Initial velocity u = 5 ms –1

Final velocity v = 2 ms–1

Work done = change in kinetic energy

W = 1/2 mv2 - 1/2 mu2

W = 1/2 m(v2 - u2)

W = 1/2 X 20(22 - 52)

W = 10 X (4-25)

W = -210J

Buy Latest Books

Teacher's Corner