Force and Motion (Class 8 Science)

Learn about forces, motion, Newton's laws, and friction. These fundamental concepts explain how objects move and interact with their environment.

Force and Motion (Class 8 Science)

Learn about forces, motion, Newton's laws, and friction. These fundamental concepts explain how objects move and interact with their environment.

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TL;DR: Learn about forces, motion, Newton's laws, and friction. These fundamental concepts explain how objects move and interact with their environment.

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Learn about forces, motion, Newton's laws, and friction. These fundamental concepts explain how objects move and interact with their environment.

Force and Motion MCQs with Answers & Explanations

Q1. What is force?

  1. Resistance of an object
  2. Speed of an object
  3. Energy of an object
  4. A push or pull that changes motion ✓ (correct)

Explanation: Force is a push or pull exerted on an object that can change its state of motion, direction, or shape. It is measured in Newtons.

Q2. Which of Newtons laws states that an object at rest will remain at rest unless acted upon by a force?

  1. First law of motion ✓ (correct)
  2. Third law of motion
  3. Law of gravitation
  4. Second law of motion

Explanation: Newtons First Law states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force. This is the law of inertia.

Q3. What is friction?

  1. A force that aids motion
  2. A force that opposes motion between surfaces in contact ✓ (correct)
  3. The tendency to remain in motion
  4. The weight of an object

Explanation: Friction is the resistance between two surfaces in contact when one slides over the other. It always opposes motion and can be static or kinetic.

Q4. How does friction affect the motion of objects?

  1. Has no effect
  2. Increases speed
  3. Decreases speed ✓ (correct)
  4. Increases mass

Explanation: Friction opposes motion and causes objects to slow down or stop. It converts kinetic energy into heat energy.

Q5. According to Newtons Second Law, what is the relationship between force, mass, and acceleration?

  1. F = m + a
  2. F = m / a
  3. F = m - a
  4. F = m x a ✓ (correct)

Explanation: Newtons Second Law states F = ma, where Force equals mass multiplied by acceleration. Greater force produces greater acceleration.

Q6. What is the SI unit of force?

  1. Newton ✓ (correct)
  2. Kilogram
  3. Joule
  4. Meter per second

Explanation: The SI unit of force is Newton (N). One Newton is the force required to accelerate a one kilogram mass at one meter per second squared.

Q7. What does Newtons Third Law of motion state?

  1. F = ma
  2. For every action there is an equal and opposite reaction ✓ (correct)
  3. Force causes acceleration
  4. Action equals reaction

Explanation: Newtons Third Law states that for every action, there is an equal and opposite reaction. Forces always occur in pairs.

Q8. What is the difference between speed and velocity?

  1. No difference
  2. Speed has direction but velocity does not
  3. Velocity has direction but speed does not ✓ (correct)
  4. Velocity is always greater

Explanation: Speed is the distance covered per unit time without direction (scalar). Velocity is displacement per unit time with direction (vector).

Q9. How can friction be reduced?

  1. Increase pressure
  2. Increase surface roughness
  3. Reduce weight
  4. Apply lubricants ✓ (correct)

Explanation: Friction can be reduced by applying lubricants like oil or grease that create a smooth layer between surfaces, or by polishing surfaces.

Q10. What is acceleration?

  1. Change in velocity per unit time ✓ (correct)
  2. Time taken
  3. Distance traveled
  4. Speed of an object

Explanation: Acceleration is the rate of change of velocity per unit time. It can be positive (speeding up), negative (slowing down), or change in direction.

Frequently Asked Questions

Why is friction sometimes helpful and sometimes harmful?

Friction is helpful for walking, writing, and braking vehicles. It is harmful when it causes energy loss in machinery and engines. Understanding friction helps us use it appropriately.

What is the difference between static and kinetic friction?

Static friction prevents an object from moving when a force is applied. Kinetic friction acts when an object is already moving. Static friction is usually greater than kinetic friction.

More Class 8 Science MCQs

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