1.

Introduction to Friction
Q1: What is friction?

A: Friction is a force that opposes motion or tries to stop the movement of one surface over
another.

Q2: How does friction affect moving objects?

A: Friction slows down moving objects and eventually stops them if no external force is
applied.

Q3: What is the origin of the word "friction"?

A: The word "friction" comes from the Latin word "fricare", which means "to rub."

Q4: Why does a vehicle slow down when brakes are applied?

A: When brakes are applied, friction between the brake pads and the tires increases, reducing
speed and eventually stopping the vehicle.

Q5: Why does a rolling ball stop after some time?

A: The friction between the ball and the ground opposes its motion, making it lose energy
and come to a halt.

Q6: What would happen if there were no friction?

A: Without friction, objects would never stop moving and would continue in the direction of
applied force unless another force acted on them.
2. Effects of Friction
Q7: How does friction produce heat?

A: When two surfaces rub against each other, the motion generates heat due to the
resistance between the surfaces.

Q8: Can you give an example of friction producing heat?

A: Rubbing your palms together generates warmth because of friction.

Q9: How does friction cause wear and tear?

A: Continuous rubbing of surfaces over time reduces their size and changes their shape, like
how an eraser gets smaller after repeated use.

3. Factors Affecting Friction

A:

1. Nature of surfaces in contact

Q11: Why does friction depend on the nature of the surface?

A: Rough surfaces have more irregularities that interlock, increasing friction, while smooth
surfaces have fewer irregularities, reducing friction.

Q12: Why do rough surfaces create more friction?

A: Rough surfaces have tiny bumps that get stuck against each other, making movement
harder.

Q13: How does the weight of an object affect friction?

A: Heavier objects press harder against a surface, increasing the frictional force.
Q14: Why is it harder to push a heavy box than a light box?

A: A heavier box has more weight, which increases friction, making it harder to move.

Q15: How does interlocking of surfaces affect friction?

A: When two surfaces come into contact, their microscopic irregularities interlock, increasing
friction.

4. Friction and Surface Area

A: No, friction is independent of surface area as long as the weight remains unchanged.

Q17: What happens when two objects of the same weight but different surface
areas are pushed?

A: The force of friction remains the same because weight is the primary factor affecting
friction, not surface area.

Q18: Why does changing the shape of an object not affect friction?

A: As long as the weight and surface roughness remain the same, the total frictional force
does not change.

5. Types of Friction
Q19: What are the three types of friction?

A:

1. Static Friction – Friction between two surfaces when they are not moving.
2. Sliding Friction – Friction when one surface slides over another.
3. Rolling Friction – Friction when an object rolls over a surface.
Q20: What is static friction?

A: Static friction is the force that prevents an object from moving when a force is applied.

Q21: Why does static friction increase as we apply more force?

A: Static friction increases proportionally to the applied force until it reaches its limit, after
which the object starts moving.

Q22: What is sliding friction?

A: Sliding friction occurs when one surface slides over another, requiring a force to keep the
motion going.

Q23: How does sliding friction compare to static friction?

A: Sliding friction is less than static friction because once an object starts moving, less force is
needed to keep it moving.

Q24: What is rolling friction?

A: Rolling friction occurs when an object rolls over a surface, like wheels on a road.

Q25: Why is rolling friction less than sliding friction?

A: Rolling objects experience less resistance than sliding objects because the area of contact
is smaller.

6. Static and Sliding Friction

A: Static friction is the force that acts between two objects in contact when they are not
moving.

Q27: When is static friction at its maximum?

A: Static friction reaches its maximum just before an object starts moving.
Q28: How does static friction help mountaineers climb?

A: Static friction between the rocks and their hands or feet provides grip, preventing them
from slipping.

Q29: What is sliding friction?

A: Sliding friction occurs when two surfaces slide over each other.

Q30: How does sliding friction compare to static friction?

A: Sliding friction is weaker than static friction, meaning once an object starts moving, it
requires less force to keep it in motion.

Q31: Give an example of sliding friction in daily life.

A: Writing with a pen involves sliding friction, as the pen tip moves smoothly over paper
while leaving a mark.

7. Rolling Friction
Q32: What is rolling friction?

A: Rolling friction is the force that opposes motion when an object rolls over a surface.

Q33: Why is rolling friction lower than sliding friction?

A: Rolling objects have less contact with the surface at any given time, reducing resistance.

Q34: How did people in ancient times reduce friction?

A: They used rollers to move heavy objects, which were later replaced by wheels.

Q35: How do modern machines reduce sliding friction?

A: Many machines use ball bearings to replace sliding friction with rolling friction.
8. Advantages of Friction
Q36: Why is friction necessary for walking?

A: Friction between our feet and the ground prevents slipping and allows movement.

Q37: How does friction help in sports?

A: Football boots have studs that provide better grip, making it easier to run.

Q38: How does friction help in stopping a bicycle?

A: Pressing the brakes increases friction between the brake pads and wheels, slowing the
bicycle.

Q39: How does friction help in lighting a matchstick?

A: The friction between the matchstick tip and the matchbox surface produces heat, igniting
the matchstick.

Q40: How does friction help musicians?

A: A violin produces music due to the friction between the bow and strings.

Q41: How does friction allow us to write?

A: The tip of a pen or pencil rubs against paper, creating marks due to friction.

Q42: How does friction help in sharpening a pencil?

A: The metallic blade of a sharpener rubs against the pencil, removing wood layers.

Q43: How does friction help in cutting wood?

A: A carpenter’s saw moves against wood, creating enough friction to cut through it.
9. Disadvantages of Friction
Q44: How does friction make rowing a boat harder?

A: The water resists movement, slowing down the boat and requiring more effort to row.

Q45: How does friction reduce machine efficiency?

A: Moving parts in machines experience friction, generating heat and energy loss.

Q46: How does friction cause wear and tear in vehicles?

A: Continuous contact between the tyres and the road wears out the tyres over time.

Q47: How does friction damage machine parts?

A: Friction heats up moving parts, causing them to get damaged or require maintenance.

10. Methods of Reducing Friction

A: Friction can cause wear and tear, overheating, and energy loss, making it necessary to
reduce in certain situations.

Q49: How does sprinkling powder reduce friction?

A: Powder, like boric acid on a carrom board, smoothens the surface and reduces friction.

Q50: How does polishing a surface reduce friction?

A: Polishing removes irregularities and roughness, making the surface smoother and reducing
friction.

Q51: How do ball bearings reduce friction?

A: Ball bearings change sliding motion into rolling motion, which has much less friction.
Q52: How do rollers help in reducing friction?

A: Rollers reduce the surface area in contact and allow objects to move smoothly, reducing
friction.

Q53: Why are lubricants used in machines?

A: Lubricants like oil and grease reduce friction by forming a smooth layer between surfaces.

Q54: How does oil reduce friction between machine parts?

A: Oil reduces direct contact between metal parts, preventing wear and overheating.