Advertisements
Advertisements
Question
A ball of mass 0.5 kg slows down from a speed of 10 m s−1 to that of 6 m s−1. Calculate the change in the kinetic energy of the ball.
Advertisements
Solution
Mass of ball = 0.5 kg
Initial velocity = 10 m s−1
Final velocity = 6 m s−1
∴ Initial K.E. = `1/2 mv^2`
= `1/2 xx 0.5 xx 10 xx 10`
= 25 J
Final K.E. = `1/2 mv^2`
= `1/2 xx 0.5 xx 6 xx 6`
= 9 J
Change in K.E. = 25 – 9 = 16 J
∴ K.E. decreases by 4 J
∴ The change in the kinetic energy of the ball is 16 J.
APPEARS IN
RELATED QUESTIONS
An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.
Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h?
Write the expression for the kinetic energy of a body explaining the meaning of the symbols used.
A car is moving with a speed of 15 km h-1 and another identical car is moving with a speed of 30 km h-1. Compare their kinetic energy.
A truck weighing 1000 kgf changes its speed from 36 km h-1 to 72 km h-1 in 2 minutes. Calculate:
- the work done by the engine and
- its power (g = 10 m s-2)
By how much will the kinetic energy of a body increase if its speed is doubled?
On a level road, a scooterist applies brakes to slow down from a speed of 10 m/s to 5 m/s. If the mass of the scooterist and the scooter be 150 kg, calculate the work done by the brakes. (Neglect air resistance and friction)
A horse and a dog are running with the same speed. If the weight of the horse is ten times that of the dog, What is the ration of their kinetic energies?
Derive the formula for the kinetic energy of an object of mass m, moving with velocity v.
A car of mass 120 kg is moving at a speed 18 km/h and it accelerates to attain a speed of 54 km/h in 5 seconds. Calculate:
- the work done by the engine.
- the power of the engine.
