Understanding the nature of friction in Friction – Class 8 Science Experiment

Chapter Name: Friction

Activity Name: Understanding the nature of friction in Friction

Activity Description:

The aim of this experiment is to understand the nature of friction, particularly static friction, between a small wooden block and a toy trolley. By varying the weight on a weight hanger attached to the trolley, we observe the changes in the motions of both the block and the trolley.

Required Items:

1. Toy trolley
2. Small wooden block
3. Inextensible string
4. Weight hanger
5. Weights (various masses)
6. Pulley
7. Table

Step by Step Procedure:

1. Place a small wooden block on the toy trolley.
2. Tie an inextensible string to the toy trolley and pass it over a pulley.
3. Fix the other end of the string to the weight hanger.
4. Place a small weight on the weight hanger.
5. Observe the motions of the block and the trolley as you add weight to the hanger.
6. Note the changes in the position and motion of the block and the trolley.

Experiment Observations:

1. Initially, the block on the trolley remains at rest with respect to the trolley’s surface but is in motion with respect to the table’s surface.
2. As the weight on the hanger increases, the trolley with the block moves towards the left with an acceleration.
3. The force of friction between the trolley’s surface and the block acts in the direction of motion, trying to keep the block at rest with respect to the trolley’s surface.
4. The block, in turn, applies a force on the trolley in the opposite direction, trying to move towards the right.
5. With increasing weight on the hanger, the trolley’s acceleration increases, and at a certain limiting acceleration or weight, the block comes into motion in the reverse direction. This means there is relative motion between the trolley’s surface and the block.

Precautions:

1. Ensure the surface of the table is clean and smooth to minimize unwanted friction.
2. Make sure the string and pulley are set up properly to allow smooth movement.
3. Carefully add weights to the hanger to avoid sudden jerks.

Lesson Learnt from Experiment:

The experiment demonstrates the concept of static friction between the block and the trolley’s surface, which resists relative motion. As the applied force (by increasing the weight on the hanger) exceeds the limit of static friction, the block starts moving.

The experiment also highlights that friction plays a crucial role in keeping objects at rest or in motion, and it depends on factors such as the nature of surfaces and the applied force.