# Conservation of mechanical energy in Work And Energy – Class 9 Science Experiment

## Activity Name: Conservation of mechanical energy in Work And Energy

### Activity Description:

In this experiment, we will demonstrate the conservation of mechanical energy using a pendulum.

By observing the motion of a swinging pendulum, we will show that the sum of potential energy and kinetic energy remains constant at any point during the oscillation, as long as there is negligible energy loss due to air resistance.

### Required Items:

1. A long thread (approximately 50-60cm)
2. A small heavy object (metal ball, for example)
3. A nail fixed to the wall

### Step by Step Procedure:

1. Attach the small heavy object (metal ball) to one end of the long thread.
2. Tie the other end of the thread to a nail fixed on the wall.
3. Pull the object (bob of the pendulum) to one side to position A1 and then release it.
4. Observe the motion of the swinging pendulum.

### Experiment Observations:

• The bob swings towards the opposite side and reaches position A2.
• The motion repeats in a back-and-forth oscillation.
• The potential energy of the bob is minimum at position A and maximum at position A1 due to the difference in height.
• As the bob moves from position A1 to A, its potential energy decreases, and its kinetic energy starts increasing.
• At position A, the kinetic energy of the bob is maximum, and its potential energy is minimum.
• The potential energy increases as the bob proceeds from position A to A1 and becomes maximum at position A2.
• Neglecting energy loss due to air resistance, the sum of potential and kinetic energy remains constant at any point during the pendulum’s motion.

### Precautions:

1. Ensure that the thread and the attachment points are secure to avoid accidents.
2. Make sure the pendulum has enough space to swing freely without hitting any obstacles.
3. Minimize air resistance by conducting the experiment in a still environment.
4. Be cautious when releasing the pendulum to avoid any sudden movements that could affect the observations.

### Lesson Learnt from Experiment:

The experiment demonstrates the principle of conservation of mechanical energy in a swinging pendulum system. Despite the continuous interchange between potential and kinetic energy during the oscillation, the total mechanical energy of the system remains constant in the absence of significant energy losses.