Friction - 1 - UPSC Sci & Tech Free MCQ Test with solutions

We sprinkle powder on carrom board to make the surface of the board smooth. This reduces the friction between the surface of the carrom board, the striker and the coins. As a result, the coins and the striker can move easily on the carrom board.

• Friction comes into play when irregularities present in the surfaces of two objects in contact get interlocked with each other.
• In sliding, the time given for interlocking is very small. Hence, the interlocking is not strong.
• Therefore, less force is required to overcome this interlocking. Because of this reason, sliding friction is less than static friction.

A spring balance is used for measuring force.
- Working Principle: It operates on Hooke's Law, which states that the force exerted by a spring is directly proportional to the displacement of the spring.
- Usage: When an object is attached, the spring stretches, and the amount of stretch correlates with the force applied, which is often related to the object's weight.
- Units: Typically measures force in newtons (N).
Hence, the correct answer is C: Measuring force.

Grooved soles provide better grip by increasing static friction through their textured surface. This enhancement in friction leads to improved traction and helps prevent slipping.

• Static friction: The resistance between two surfaces that are not moving relative to each other.
• Textured surface: The grooved design that enhances grip.
• Traction: The grip or hold that prevents slipping.

- When a floor is wet, water creates a thin layer between your shoes and the surface.
- This layer reduces the contact area, which is essential for grip.
- Friction is the force that helps our feet push against the ground to maintain balance.
- With decreased friction on a wet surface, it’s easier to slip, making walking more difficult and potentially dangerous.
- Thus, the primary reason for difficulty is reduced friction, not changes in weight or gravitational pull.

Friction is caused by the irregularities on the two surfaces in contact. This means that when two things are touching each other, the bumps and rough parts on their surfaces stick together, making it harder to move them against each other. So, the correct answer is "Surfaces."

• When we push or pull an object, friction acts in the opposite direction to the motion.
• So, if we push a book to the right, friction acts to the left, and if we push it to the left, friction acts to the right.
• This means friction opposes the motion, trying to stop the object from moving.
• So, the statement is False.

Friction opposes the relative motion between two surfaces in contact. Frictional force acts in opposite direction of motion to slow down the speed of moving body.

Fluid friction can be minimized by giving suitable shapes to the objects moving in the fluids.

A polished marble surface has the least frictional force, hence a car will travel farther on a marble floor.

In machine, friction between moving parts is reduced by using lubricants. These lubricants stick with machine parts to make them smoother that leads to reduction in friction.

Let’s carefully look at the situation.

The boy is pushing the box from right to left.

• This means the applied force is directed towards the left (→ box moves left).
• Friction is a force that always opposes motion (or the tendency of motion).

So, if the push is from right to left, then the frictional force must act opposite to it, i.e. from left to right.

Why not other options?

• Option a (right to left): That’s the direction of the applied force, not friction.
• Option c (downwards): That’s the direction of weight (gravity), not friction.
• Option d (upwards): That’s the direction of normal reaction from the floor, not friction.

Correct Answer:

b) from left to right (→)

When objects move through fluids like air or water, they experience a force called frictional force. This force makes it harder for objects to move smoothly through the fluid.