1. What is work in mechanics?

Work in mechanics is said to be done when an object moves through a certain distance under the influence of an applied force. The SI unit of work is joule (J or Nm).

2. What are the two essential conditions for work to be done?

The two essential conditions for work to be done are:

(i) application of some force on the object,

(ii) displacement of the object in the direction of a force.

3. A force of 50 N is applied to a block of mass 10 kg, which moves a distance of 5 meters. What is the work done by the force on the block?

Work done = force x displacement x cosθ

Here, force = 50 N

displacement = 5 m

cosθ = 1 (as force and displacement are in the same direction)

Work done = 50 x 5 x 1 = 250 J

4. What is energy in physics?

Energy in physics is defined as the capacity of an object to do work. The unit of energy is the same as the unit of work, i.e., joule (J).

5. What are the different forms of energy?

The different forms of energy are mechanical energy, heat energy, electrical energy, light energy, chemical energy, nuclear energy, etc.

6. What is kinetic energy?

Kinetic energy is the energy possessed by an object by virtue of its state of motion. The formula for calculating kinetic energy is K.E. = (1/2)mv², where K.E. represents the kinetic energy of an object in joules (J), m represents the mass of the object in kilograms (kg), and v represents the velocity of the object in meters per second (m/s).

7. A bullet of mass 10 g is moving with a velocity of 500 m/s. Calculate its kinetic energy.

Kinetic energy = (1/2)mv²

Here, mass = 10 g = 0.01 kg, velocity = 500 m/s

Kinetic energy = (1/2) x 0.01 x (500)²

Kinetic energy = 1250 J

8. What is potential energy?

Potential energy is the energy present in an object by virtue of its position or configuration or change thereof. The formula for calculating potential energy is P.E. = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height of the object above a reference point. The unit of potential energy is joules (J).

9. What is gravitational potential energy?

Gravitational potential energy is the work done in raising an object against gravity from the ground to a point above it. It is a form of potential energy, and the simplest one is gravitational potential energy.

10. A body of mass 2 kg is thrown vertically upwards with a velocity of 20 m/s. Calculate its potential energy at a height of 10 m.

Potential energy = mgh

Here, mass = 2 kg, g = 9.8 m/s², h = 10 m

Potential energy = 2 x 9.8 x 10

Potential energy = 196 J

11. What is the law of conservation of energy?

The law of conservation of energy states that energy can neither be created nor destroyed, but can only be transformed from one form to another, such that the total energy before and after the transformation remains exactly the same.

12. Is the law of conservation of energy valid in all situations?

Yes, the law of conservation of energy is valid in all situations and for all sorts of transformations.

13. What is power in physics?

Power in physics is the rate of doing work or the rate of transfer of energy.The SI unit of power is a watt.

Power = work / time

P = W/t

14. A motor lifts a 100 kg load to a height of 10 meters in 5 seconds. Calculate the power of the motor.

Power = work done / time taken

Work done = mgh = 100 x 10 x 5 = 5000 J

Time taken = 5 seconds

Power = 5000 / 5 = 1000 watts or 1 kW

15. What is the difference between kinetic energy and potential energy?

Kinetic energy is the energy possessed by an object by virtue of its state of motion, while potential energy is the energy present in an object by virtue of its position or configuration.

16. What is the relationship between work and energy?

Energy is the capacity to do work, and work is the transfer of energy from one object to another.

17. What is the difference between positive and negative work?

Work is considered positive if the displacement of the object is along the direction of force applied. On the other hand, work is taken as negative if the displacement of the object is in a direction opposite to the direction of force applied.