Friction Part 2: MCQs (Q26–Q50)
🌀 Friction – MCQs for Class 8 Science
Part 2: Q26–Q50
Q26. Friction is caused due to:
A) Smoothness of surfaces
B) Interlocking of irregularities
C) Gravitational force
D) Pressure of air
✅ Correct Answer: B) Interlocking of irregularities
Explanation:
- A) Smooth surfaces reduce friction.
- B) ✔ Microscopic irregularities interlock → friction.
- C, D – Not the cause.
Q27. Sliding friction is always:
A) Equal to static friction
B) Greater than static friction
C) Less than static friction
D) Independent of surfaces
✅ Correct Answer: C) Less than static friction
Explanation:
- C) ✔ Once object starts moving, less force is needed.
Q28. Which of these is a disadvantage of friction?
A) Helps in walking
B) Causes wear of machine parts
C) Helps to grip things
D) Allows vehicles to move
✅ Correct Answer: B) Causes wear of machine parts
Explanation:
- B) ✔ Constant rubbing damages engines, tyres, etc.
Q29. Which of these reduces friction?
A) Sand
B) Grease
C) Rough surface
D) Pressure
✅ Correct Answer: B) Grease
Explanation:
- B) ✔ Lubricants like grease reduce resistance.
Q30. Fluid friction is reduced by:
A) Making surfaces rough
B) Increasing surface area
C) Streamlining the shape
D) Adding more load
✅ Correct Answer: C) Streamlining the shape
Explanation:
- C) ✔ Streamlined body reduces drag.
Q31. Friction is useful in:
A) Writing with chalk
B) Lighting matchsticks
C) Walking
D) All of these
✅ Correct Answer: D) All of these
Explanation:
- D) ✔ Everyday activities possible only due to friction.
Q32. Which of the following produces heat due to friction?
A) Brakes of vehicles
B) Rubbing of hands
C) Matchstick ignition
D) All of these
✅ Correct Answer: D) All of these
Explanation:
- D) ✔ Heat is generated in all cases due to friction.
Q33. Which friction is desirable in machines?
A) Static friction
B) Sliding friction
C) Rolling friction
D) Fluid friction
✅ Correct Answer: C) Rolling friction
Explanation:
- C) ✔ Rolling friction is least, hence desirable in machines.
Q34. The brake pads in vehicles work due to:
A) Rolling friction
B) Fluid friction
C) Sliding friction
D) Non-contact force
✅ Correct Answer: C) Sliding friction
Explanation:
- C) ✔ Pads rub wheels → sliding friction stops motion.
Q35. When a body is at rest, the friction acting on it is:
A) Sliding friction
B) Rolling friction
C) Static friction
D) Fluid friction
✅ Correct Answer: C) Static friction
Explanation:
- C) ✔ Static friction resists initial motion.
Q36. Why do gymnasts use powder on their hands?
A) To make hands shiny
B) To reduce weight
C) To increase grip by increasing friction
D) To decrease grip
✅ Correct Answer: C) To increase grip by increasing friction
Explanation:
- C) ✔ Chalk powder increases roughness → more friction.
Q37. Why are soles of shoes grooved?
A) To look good
B) To reduce cost
C) To increase friction with ground
D) To make them lighter
✅ Correct Answer: C) To increase friction with ground
Explanation:
- C) ✔ Grooves prevent slipping by increasing grip.
Q38. Why do vehicles use ball bearings?
A) To increase sliding friction
B) To reduce rolling friction
C) To increase weight
D) To increase drag
✅ Correct Answer: B) To reduce rolling friction
Explanation:
- B) ✔ Ball bearings reduce resistance and save energy.
Q39. Which has the maximum friction?
A) Rolling
B) Sliding
C) Static
D) Fluid
✅ Correct Answer: C) Static
Explanation:
- C) ✔ Static friction > sliding > rolling.
Q40. Which has the minimum friction?
A) Static
B) Sliding
C) Rolling
D) Limiting
✅ Correct Answer: C) Rolling
Explanation:
- C) ✔ Rolling friction is least.
Q41. Which of these is an advantage of friction?
A) Produces noise
B) Produces heat
C) Helps in walking
D) Causes wear and tear
✅ Correct Answer: C) Helps in walking
Explanation:
- C) ✔ Friction between ground and feet allows walking.
Q42. Which factor increases sliding friction?
A) Smoother surface
B) Lubrication
C) Rougher surface
D) Use of ball bearings
✅ Correct Answer: C) Rougher surface
Explanation:
- C) ✔ Roughness increases resistance.
Q43. Friction can be reduced by:
A) Using lubricants
B) Using wheels
C) Polishing
D) All of these
✅ Correct Answer: D) All of these
Explanation:
- D) ✔ All methods reduce resistance.
Q44. The resistance faced by a car moving in air is called:
A) Air drag
B) Static friction
C) Rolling friction
D) Lubrication
✅ Correct Answer: A) Air drag
Explanation:
- A) ✔ Drag in air is air resistance.
Q45. Why is friction considered a “necessary evil”?
A) Only harmful
B) Only useful
C) Both useful and harmful
D) Neither useful nor harmful
✅ Correct Answer: C) Both useful and harmful
Explanation:
- C) ✔ Needed for daily life but causes energy loss.
Q46. Why are streamlined shapes given to ships and airplanes?
A) To increase beauty
B) To reduce drag
C) To increase friction
D) To increase weight
✅ Correct Answer: B) To reduce drag
Explanation:
- B) ✔ Streamlining minimizes fluid resistance.
Q47. Which of these reduces friction in machines?
A) Grease
B) Oil
C) Ball bearings
D) All of these
✅ Correct Answer: D) All of these
Explanation:
- D) ✔ All help reduce energy loss.
Q48. Which type of friction acts when wheels of a moving vehicle roll on road?
A) Rolling friction
B) Sliding friction
C) Static friction
D) Fluid friction
✅ Correct Answer: A) Rolling friction
Explanation:
- A) ✔ Wheels = rolling friction.
Q49. Matchsticks are made of wood coated with chemicals so that:
A) They look attractive
B) They can be reused
C) Friction produces enough heat to ignite
D) They are stronger
✅ Correct Answer: C) Friction produces enough heat to ignite
Explanation:
- C) ✔ Friction heat starts burning.
Q50. The heat generated in machine parts due to friction causes:
A) Greater efficiency
B) Energy loss and wear
C) Increase in lifespan
D) Cooling of parts
✅ Correct Answer: B) Energy loss and wear
Explanation:
- B) ✔ Heat reduces efficiency and damages machines.
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