Let's go through each question one by one and solve them with explanations.
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Q.10. Which of the following is not a method of reducing friction?
a) By polishing the surfaces
b) By using lubricants (like oil)
c) By using ball bearings or roller bearings
d) Spreading sand on icy roads
✔ Correct answer: d) Spreading sand on icy roads
Explanation:
- Polishing surfaces reduces roughness, thus reducing friction.
- Lubricants like oil create a slippery layer between surfaces, reducing friction.
- Ball or roller bearings convert sliding friction into rolling friction, which is much lower.
- However,
spreading sand on icy roads increases friction, not reduces it. It improves grip (especially for tires), so this is actually a method to *increase* friction for safety.
So,
d) is
not a method of reducing friction — it's the opposite.
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Q.11. What is the weakest type of friction that occurs between solid surfaces?
a) Sliding
b) Rolling
c) Fluid
d) Static
✔ Correct answer: b) Rolling
Explanation:
Among solid surfaces:
-
Static friction is the strongest (it prevents motion from starting).
-
Sliding friction is less than static but still significant.
-
Rolling friction is much weaker than both sliding and static friction — that’s why wheels are used to move heavy objects easily.
-
Fluid friction (e.g., air or water resistance) is not between solid surfaces.
So,
rolling friction is the weakest among solid-solid interactions.
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Q.12. What form of energy does friction always produce?
a) Heat
b) Kinetic
c) Chemical
d) Potential
✔ Correct answer: a) Heat
Explanation:
Friction converts kinetic energy into
thermal energy (heat). This happens due to the microscopic collisions and deformation at contact surfaces. For example, rubbing your hands together warms them up — that’s heat from friction.
While other forms of energy may be involved in a system,
friction always produces heat as a result of energy dissipation.
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Q.13. Friction is a __________ force.
a) spring
b) contact
c) magnetic
d) non-contact
✔ Correct answer: b) contact
Explanation:
Friction arises only when two surfaces are in
direct physical contact. It opposes relative motion between them. Unlike magnetic or gravitational forces, which act at a distance (non-contact), friction requires touch.
So, friction is a
contact force.
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Q.14. Falling toward Earth with a parachute is an example of what type of friction?
a) Sliding
b) Rolling
c) Fluid
d) Static
✔ Correct answer: c) Fluid
Explanation:
When a person falls with a parachute, they move through the
air, which is a fluid. The resistance offered by the air is called
fluid friction (specifically, air resistance). Since air is a fluid (gas), this is an example of
fluid friction.
- Sliding and rolling involve solid surfaces.
- Static friction applies when there’s no motion between surfaces.
Thus,
fluid friction is correct.
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✔ Final Answers:
| Question | Answer |
|--------|--------|
| Q.10 | d) Spreading sand on icy roads |
| Q.11 | b) Rolling |
| Q.12 | a) Heat |
| Q.13 | b) contact |
| Q.14 | c) Fluid |
Let me know if you'd like diagrams or further explanation!
Parent Tip: Review the logic above to help your child master the concept of friction worksheet pdf.
