Energy

An object of mass, $m$ is moving with a constant velocity, $v$. How much work should be done on the object in order to bring the object to rest?  

Assertion: If velocity of a moving body is increased to double, then its kinetic energy increases four times.

Reason: Kinetic energy is directly proportional to the square of velocity.

The explosion at Krakatoa is estimated to have released the energy equivalent to $200 \mathrm{million} \mathrm{tonnes}$ of TNT. The first nuclear detonation-the Trinity test -yielded an equivalent of $22 \mathrm{thousand} \mathrm{tonnes}$ of TNT. How many times more powerful was the explosion at Krakatoa?

A car travels along a flat road. It has $50 \mathrm{billion} \mathrm{J}$ of kinetic energy. Every second, air resistance and other frictional forces cause it to lose$1 \mathrm{billion} \mathrm{J}$  of energy. If the car is to travel at a constant speed, how much energy will the engine have to convert to kinetic energy every second?

A toy car has a kinetic energy of $10 \mathrm{J}$. It rolls up a slope and at the top it has $3 \mathrm{J}$ of gravitational potential energy and $5 \mathrm{J}$ of kinetic energy. How much energy has the car lost through friction?

Name the kind of energy used in the following.

Name the kind of energy used in the following.

When a driver wants to stop a car, he presses the brake pedal. The brakes applied, which use friction to slow the car to a stop. Which of the following energy transformations occurs as a car brakes?

A driver parks his car on a hill but forgets to put brakes on. The car starts to roll down the hill. Which of the following energy transformation occurs as the car rolls down the hill?

A body of $12 \mathrm{kg}$ mass is placed at a certain height from the surface of earth. If its potential energy is $480 \mathrm{J}$, then what will be its height with respect to earth's surface? $(g=10 {\mathrm{ms}}^{-2})$

Loudspeaker converts electrical energy to _____ (sound/heat) energy.

There is a slight temperature difference between the waterfall at the top and at the bottom because

A stone of mass $500 \mathrm{g}$is thrown vertically upwards with a velocity of $15 \mathrm{m}/\mathrm{s}$. Calculate the potential energy (in joules) at the greatest height.

A body of mass $60 \mathrm{kg}$ has the momentum $3000 \mathrm{kg} {\mathrm{ms}}^{-1}.$ Calculate the kinetic energy and speed of the body.

A ball of mass $0.5 \mathrm{kg}$ slows down from a speed of $5 {\mathrm{ms}}^{-1}$ to that of $2 {\mathrm{ms}}^{-1}$. Calculate the change in kinetic energy of the ball. 

Calculate the kinetic energy of a body of mass $0.1 \mathrm{kg}$and momentum $20 {\mathrm{kgms}}^{-1}.$ (in joules)

A bullet of mass $5 \mathrm{g}$ travels with a speed of $500 {\mathrm{ms}}^{-1}$. If it penetrates a fixed target which offers a constant resistive force of $1000 \mathrm{N}$ to the motion of the bullet, find the initial kinetic energy (in joules) of the bullet.

Two bodies A and B of masses $4 \mathrm{kg}$ and $16 \mathrm{kg}$ respectively have same kinetic energy. The ratio of velocity of A and B is:

If velocity of a moving body becomes one-fourth while the mass remains constant, the kinetic energy of the body

A stone is thrown upwards as shown in the diagram. When it reaches P, the _____ energy of the stone will be maximum.