Energy

What is the origin of sunlight in the universe?

Derive that mechanical energy is always constant in the case of a freely falling body.

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?  

What is the difference between energy and work done?

A person does $5000 \mathrm{J}$ of work in climbing a tree of height $5 \mathrm{m}$. Calculate the mass of the person.

A body of mass $2 \mathrm{kg}$ is projected vertically up with the velocity of $20 {\mathrm{ms}}^{-1}$. If the energy spent in overcoming air resistance is $100 \mathrm{J}$, the maximum height attained by it is ($\mathrm{g}=10 {\mathrm{ms}}^{-2}$)

Two bodies of the same mass have velocities in the ratio 2:3. The ratio of their kinetic energies will be

How sound is produced in a radio or television?

Define kinetic energy. Derive an expression for kinetic energy of a body of mass m moving with a velocity v.

What happens to the molecules when the ice starts to melt$?$

What is kinetic energy?

The hydraulic press given in the figure is used to raise the mass M through a height of $0.5 \mathrm{cm}$ by performing $500 \mathrm{J}$ of work at the small piston. The diameter of the large piston is $10 \mathrm{cm}$, while that of the smaller one is $2 \mathrm{cm}$. The mass M is:

If a bullet of mass $80 \mathrm{g}$ moves with a velocity of $700 \mathrm{m} {\mathrm{s}}^{-1}$. It penetrates $25 \mathrm{cm}$ into a target which is not moving and then comes to rest. Find the kinetic energy possessed by the bullet and also the average retarding force offered by the target. 

What is gravitational potential energy? Derive its equation.

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.