# NCERT Question 13 - Chapter 9 Class 9 - Force and Laws Of Motion

Last updated at April 16, 2024 by Teachoo

NCERT Questions

NCERT Question 1
Important

NCERT Question 2 Important

NCERT Question 3 Important

NCERT Question 4 Important

NCERT Question 5 Important

NCERT Question 6 Important

NCERT Question 7 Important

NCERT Question 8

NCERT Question 9

NCERT Question 10 Important

NCERT Question 11

NCERT Question 12 Important

NCERT Question 13 You are here

NCERT Question 14

NCERT Question 15 Important

NCERT Question 16 Important

NCERT Question 17 Important

NCERT Question 18 Important

Class 9

Chapter 9 Class 9 - Force and Laws Of Motion

Last updated at April 16, 2024 by Teachoo

NCERT Question 13 A hockey ball of mass 200 g travelling at 10 m s–1 is struck by a hockey stick so as to return it along its original path with a velocity at 5 m s–1. Calculate the magnitude of change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick. Given Mass of the hockey ball = m = 200 g = 200/1000 = 0.2 kg Initial velocity of the ball = u = 10 m/s Final velocity of the ball = v = −5m/s Final velocity is negative because it is in the opposite direction Initial Momentum Initial momentum = Mass × Initial velocity = m × u = 0.2 × 10 = 2 kg m/s Final Momentum Final momentum = Mass × Final velocity = m × b = 0.2 × −5 = – 1 kg m/s Change in momentum = Final momentum − Initial momentum = −1 − 2 = −3 kg m/s Thus, the magnitude of change in momentum is 3 kg m/s (Magnitude is only value, without the sign)