calculate the work done by the brakes of a car of mass 1000 kg when its speed is reduced from 20 metre per second to 10 metre per second ?
Answers
Answer:
Answer of this question 150 KJ
Answer:
The work done by the brakes of a car is -1,50,000 J.
Explanation:
By the work-energy theorem, the work done on an object will be equal to the change in its kinetic energy. So we need to calculate the change in kinetic energy of the car when it reduced its speed from 20 m/s to 10 m/s.
The mass of the car, m = 1000 Kg
The initial velocity of the car, u = 20 m/s
The final velocity of the car, v = 10 m/s
The initial kinetic energy of the car, K.E₁ = (mu²) / 2
= (1000 × 20²) / 2
= 2,00,000 J
The final kinetic energy of the car, K.E₂ = (mv²) / 2
= (1000 × 10²) / 2
= 50,000 J
∴ Work done by the breaks of the car = change in kinetic energy of the car
Work done = K.E₂ - K.E₁
= 50,000 - 2,00,000
= -1,50,000 J
The negative sign indicates that the work is done against the direction of motion.