Question

On the following occasions friction is beneficial and non-beneficial.
1. Striking a match stick on the side of a match box
2. Wear and tear of machines
3. Ability to hold objects
4. Wearing out of tyres
5. Walking
6. Loss of fuel

Answer 1

Friction is a resistive force caused when there is a relative motion between the two surfaces given that the two surfaces are irregular to each other. Friction force always tends to oppose the motion meaning it is always in the direction opposite to the motion. Friction caused by rubbing of two bodies generated wear and tear between them along with liberation heat energy.

Complete step by step answer:
When a match stick is rubbed by the side of the match box, the rubbing friction is high enough to produce a sufficient amount of heat energy that can ignite the phosphorus at the top of the match stick causing it to ignite. Thus, in this case friction is useful for ignition of the match.

In machine parts there is a sufficient rubbing between the parts. This rubbing friction causes the wearing and tearing of machine parts which causes the machine parts to withered causing malfunctioning in the machine. Thus, in this case friction is non-beneficial. When we press the object, the object exerts a normal force back to our hand. The friction force that opposes the downward motion of the object helps us to hold the object in our hand. Thus, in this case friction is beneficial.

The above diagram shows the free body diagram of holding an object, we apply the force $F$ with our hands and object balances it by applying and equal but opposite force of normal $N$ on our hands, and the friction force $\mu N$ balances the weight $W$ of the object.When a tyre moves in a road the friction force between the road and the tyre caused the grip of the tyre to lose with time. Finally, a time comes when there is no grip in the tyres, and a case arises when the rider can slip due to this faulty Tyre. Thus, in this case friction is non-beneficial.

When we walk, we exert a force in the backward direction in the ground, the ground in order to oppose the motion exerts a friction force on the forward direction. This force of friction in the forward direction causes our body to move forward. Thus, in this case friction is beneficial.

We exert a force (our weight) $W$ on the ground which the ground balances by applying a force of normal $N$ in upward direction. The backward force $F$ of our foot is balanced by the force of friction $\mu N$ in the forward direction causing our body to move forward.Loss of fuel or loss of energy is caused mainly due to the resistive force offered by friction like wind resistance or track resistance etc. Thus, this causes a low efficiency of the machines and here the friction force is non-beneficial.

Note: Friction is a necessary dissipative force which is required in our life, it is due to friction that a car wheel moves. Sometimes when we want to stop or accelerate a fast moving car the friction force causes it to slow down, causing wear of the tyres but the main aspect is to slow down the car in which friction force was successful, and thus proving to be beneficial. So, in certain cases we need to analyse the problem more deeply in order to reach a conclusion.