Frictional force between two bodies a)Adds the motion between the bodies b)Destroys the relative motion between the bodies c)Sometimes helps and sometimes opposes the motion d)Increases the relative velocity between the bodies Correct answer is option 'C'. Can you explain this answer?

Question

Answer

Friction does not always oppose motion. For eg when a car is accelerating forward , the tyres push against the road in a backward direction. Friction pushes itself in forward and the car also pushes forward. Thus friction and motion are in the same direction.
Similarly when a runner accelerates forward the shoe pushes backward, friction pushes forward and runner pushes forward. Thus both are in same direction
Hence force of friction does not always oppose motion or the tendency of motion.

Answer

Friction may slow the car down as it moves along the road, but it also is the force that enables the car to move forward. When a car's tires start to turn, the friction between the road and the tires make the car move forward. So, in this case, friction helps in motion.

Now when a car slows down, the friction between the road and the tires helps to bring the car to a stop. It is the friction between the wheels and the brake pads that causes the wheels to slow down. So, in this case, it prevents motion.

Hence, the correct answer is (b).

Answer

Explanation:

Frictional force is the force that opposes the relative motion or tendency of motion between two surfaces in contact. It is caused by the irregularities or microscopic roughness present on the surfaces in contact. The frictional force between two bodies can have different effects on their motion, depending on the circumstances.

Sometimes helps and sometimes opposes the motion:
Frictional force can sometimes help and sometimes oppose the motion between two bodies. This is because the direction of frictional force depends on the direction of the applied force and the nature of the surfaces in contact. Let's consider two scenarios to understand this:

1. Starting motion: When two bodies are at rest and an external force is applied to move one body relative to the other, the frictional force initially opposes the motion. It provides an opposing force that needs to be overcome by the applied force. However, once the applied force overcomes the static friction, the bodies start moving. At this point, the frictional force changes from static friction to kinetic friction, which opposes the motion but also helps in maintaining a constant velocity.

2. Slowing down or stopping motion: If the bodies are already in motion and an external force is applied in the opposite direction of the motion, the frictional force opposes the motion and helps in slowing down or stopping the bodies. In this case, the frictional force acts in the direction opposite to the motion, reducing the relative velocity between the bodies.

Conclusion:
In conclusion, the frictional force between two bodies sometimes helps and sometimes opposes the motion. It initially opposes the motion when the bodies are at rest or when an external force is applied in the opposite direction of the motion. However, once the bodies are in motion, the frictional force helps in maintaining a constant velocity. The specific effect of frictional force on the motion depends on the circumstances and the direction of the applied force.

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