Energy and Its Sources

Q.

Which among the following is not a good source of energy?

1. Sun

2. Wind

3. Water

4. All of these

Q. The law of conservation of energy states that:

1. Energy must be conserved and it shouldn’t be wasted.
2. The supply of energy is limited and must be conserved.
3. The total amount of energy of the system is constant.
4. Energy cannot be used faster than it is created.

Q.

State two characteristics which a source of energy must have.

Q. A ball of mass in is thrown vertically up with an initial velocity so as to reach a height h. The correct statement is:
(a) Potential energy of the ball at the ground in mgh.
(b) Kinetic energy imparted to the ball at the ground is zero.
(c) Kinetic energy of the ball at the highest point is mgh.
(d) potential energy of the ball at the highest point is mgh.

Q.

An object of mass 20 kg is raised to a height 5 m above the ground. What is its P.E.? If object is allowed to fall, find its K.E. just before touching the ground and also its K.E. when it is half way down. [3 MARKS]