Extra Questions: Class 8 Science Chapter 5 Exploring Forces

Practice questions beyond the textbook exercise, testing deeper understanding of force, weight, and buoyancy for Class 8 Science Chapter 5: Exploring Forces. These Class 8 Science Chapter 5 important questions are handy for last-minute exam practice.

Last Updated: September 23, 2026

Extra Questions: Class 8 Science Chapter 5 Exploring Forces

1. 1 (Assertion-Reason). Assertion: Mass and weight are the same thing. Reason: Both are measured using a spring balance.
   Solution: The assertion is false — mass and weight are different physical quantities (mass is fixed, weight varies with gravity); the reason is also misleading since a beam balance measures mass while a spring balance measures weight.
2. 2 (Short Answer). Name the two types of contact forces mentioned in this chapter.
   Solution: Muscular force and frictional force.
3. 3 (Applied). Two identical bar magnets are brought close with opposite poles facing each other. What happens, and is contact needed?
   Solution: They attract each other; no contact is needed, since magnetic force is a non-contact force.
4. 4 (Assertion-Reason). Assertion: A ship made of iron floats on water. Reason: The ship’s shape displaces enough water so the buoyant force equals its weight.
   Solution: Both true, and the reason correctly explains the assertion — despite iron being denser than water, the ship’s hollow shape increases the volume of water displaced.
5. 5 (Short Answer). What SI unit is weight measured in?
   Solution: Newton (N).
6. 6 (Applied). A person weighs 600 N on Earth. Estimate their approximate weight on the Moon.
   Solution: Moon’s gravity is about one-sixth of Earth’s, so weight ≈ 600÷6 = 100 N.
7. 7 (Synthesis). Why does rubbing a balloon on hair make the hair stand up, but this doesn’t happen without rubbing?
   Solution: Rubbing transfers electric charge to the balloon, giving it an electrostatic (non-contact) force that attracts the oppositely/uncharged hair strands; without rubbing, neither object is charged, so no such force exists.
8. 8 (Assertion-Reason). Assertion: A block of wood and a block of iron of the same size, placed in water, experience the same buoyant force. Reason: Buoyant force depends only on the volume of liquid displaced, not on the material’s weight.
   Solution: Both true, and the reason correctly explains the assertion — same size means same volume displaced (if both are fully submerged), giving equal buoyant force, even though only the wood may float.
9. 9 (Short Answer). Give one example of a force that can act without any contact.
   Solution: Gravitational force (or magnetic force, or electrostatic force).
10. 10 (Applied). A block resting on a rough table needs 20 N to start moving, but only 12 N to keep it moving at constant speed. What does this suggest about friction?
    Solution: It suggests friction is greater just before motion starts (static friction, resisting the initial push) than while the object is already sliding (kinetic/sliding friction, which is generally smaller).

Frequently Asked Questions

Why does it feel harder to push a loaded box across a rough floor than an empty one?
A loaded box presses down with greater weight, which increases the normal force between the box and the floor, and since friction relates to this normal force, a heavier box experiences greater frictional resistance.

How does the concept of net force explain why an object at rest stays at rest?
An object at rest stays at rest when the net force acting on it is zero, meaning all individual forces acting on it balance each other out exactly, leaving no unbalanced force to cause motion.

Written by Satish

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