## 1. Work is said to be done when:

### Answer:

### Explanation:

Work is defined as the product of force and the displacement in the direction of the force.

## 2. The ability to do work is called:

### Answer:

### Explanation:

Energy is the capability of a system to perform work.

## 3. Which of the following is a scalar quantity?

### Answer:

### Explanation:

Work has only magnitude and no specific direction, making it a scalar quantity.

## 4. If a force F displaces a body through distance d in a direction perpendicular to the direction of force, the work done is:

### Answer:

### Explanation:

Work done is zero when the force is perpendicular to the direction of displacement.

## 5. The rate of doing work or the rate of transfer of energy is defined as:

### Answer:

### Explanation:

Power is the rate at which work is done or energy is transferred.

## 6. The potential energy of a body of mass m at a height h from the ground is given by:

### Answer:

### Explanation:

Potential energy due to height is given by mgh, where g is the acceleration due to gravity.

## 7. Work-Energy theorem relates:

### Answer:

### Explanation:

The Work-Energy theorem states that the work done by all the forces acting on a body is equal to the change in its kinetic energy.

## 8. The unit of power in SI system is:

### Answer:

### Explanation:

Power is the rate of doing work, and its SI unit is Watt.

## 9. If the kinetic energy of a body is increased by 300%, the percentage increase in its momentum is:

### Answer:

### Explanation:

Since KE ∝ (momentum)^2, if KE increases by 300%, the momentum increases by the square root of 4, which is 2 or a 100% increase. Hence, the new momentum is increased by 173%.

## 10. A machine that transforms electrical energy to mechanical energy is:

### Answer:

### Explanation:

A motor converts electrical energy into mechanical energy.

## 11. The energy possessed by a body due to its position or configuration is called:

### Answer:

### Explanation:

Potential energy is the energy possessed by a body by virtue of its position or configuration.

## 12. Efficiency is defined as:

### Answer:

### Explanation:

Efficiency measures how much of the input energy is usefully converted to output.

## 13. A body falls from a height h. Just before hitting the ground, its kinetic energy is:

### Answer:

### Explanation:

As it falls, potential energy is converted to kinetic energy. Just before hitting the ground, all potential energy becomes kinetic energy, which is mgh.

## 14. Energy can be:

### Answer:

### Explanation:

According to the law of conservation of energy, energy can neither be created nor destroyed but can be transformed from one form to another.