Effects of Frictional Force

Frictional force is a force that opposes motion when two surfaces come into contact with each other. It arises due to the roughness of the surfaces and intermolecular forces between them. Frictional force has various effects on objects in motion or at rest. Let's examine the given options and identify which one is NOT an effect of frictional force.

a) The grooves of tyres flattened due to use
When a vehicle is in motion, the frictional force between the tyres and the road surface helps provide traction and allows the vehicle to move forward. Over time, the constant rubbing between the tyres and the road can cause the grooves on the tyre to flatten. This is due to the wear and tear caused by the frictional force.

b) A rolling ball coming to a halt
Frictional force plays a significant role in bringing a rolling ball to a halt. As the ball rolls on a surface, the friction between the ball and the surface opposes its motion, gradually slowing it down until it eventually comes to a stop. This effect of frictional force is commonly observed in everyday situations.

c) Leaves falling from a tree
The statement mentions that this is NOT an effect of frictional force. However, frictional force does not directly influence the falling of leaves from a tree. The primary factors responsible for leaves falling from a tree are the changing seasons and the growth of new leaves. Frictional force is not involved in this process.

d) The holding of a pencil
Frictional force plays a crucial role in holding a pencil or any other object. When we grip a pencil, the friction between our fingers and the pencil provides the necessary grip or traction to hold it firmly. Without friction, the pencil would slip out of our fingers easily.

Conclusion
Based on the explanations given above, the correct answer is option 'c' - Leaves falling from a tree. Frictional force does not directly impact the falling of leaves from a tree.