Calculate the work required to be done to stop a car of 1000 kg moving with a velocity of 36 km/hr

Last updated at June 8, 2019 by

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

Answer:

Mass of the car (m) = 1500 kg

Velocity (v) = 60 km/hr

v = 60 x 5/18

v = 16.67 m/s

The car is in motion, so its energy is,

Kinetic Energy (K.E) = 1 /2 mv2

\(\begin{array}{l}K.E = \frac{1}{2}\times 1500 \times ( 16.67)^{2}\end{array} \)

K.E = 1/ 2 × (1500) × 277.88 J

K.E = 208416.7 J

The kinetic energy of the car, when it comes to rest = 0 J

Work done on object = change in kinetic energy