# NCERT Question 17 - Chapter 11 Class 9 - Work and Energy

Last updated at June 8, 2019 by Teachoo

Last updated at June 8, 2019 by Teachoo

Transcript

NCERT Question 17 Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h? Mass of car = m = 1500 kg Velocity of the car = v = 60 km/hr = 60 × 5/18 m/s = 10 × 5/3 m/s = 50/3 m/s Conversion from km/h to m/s 1 km = 1000 m 1 hour = 60 minutes = 3600 s ∴ (1 𝑘𝑚)/ℎ = (1000 𝑚)/(3600 𝑠) ∴ 1 km/h = 5/18 m/s Work done = Kinetic energy of the car I nitial Kinetic energy = 1/2 mv2 = 1/2 × (1500) × (50/3)^2 = 1/2 × 1500 × (50/3×50/3) = 1/2 × 1500 × 2500/9 = (500 × 2500)/(3 × 2) = (250 × 2500)/3 = 208333.3 J Since the car eventually stops Final Kinetic Energy = 0 Now, Work done = Change in Kinetic energy = 208333.3 – 0 = 208333.3 J Work done is 208333.3 J

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Class 9

Chapter 11 Class 9 - Work and Energy

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.