How Forces Affect Motion MCQs

Q1. Which is a non-contact force?

• A.gravitational force between the Earth and a falling apple
• B.friction between tyres and road
• C.the push of a hand on a door
• D.tension in a rope pulling a cart

Answer: A. gravitational force between the Earth and a falling apple

NCERT fact (physics, chapter 'How Forces Affect Motion'): Gravitation acts at a distance without contact - a non-contact force. Why option A fits - Correct. Distractor analysis: option B) 'friction between tyres and road' misses the point - Friction is a contact force; option C) 'the push of a hand on a door' is wrong because A push by contact is a contact force. Final answer - A) gravitational force between the Earth and a falling apple.

Q2. A force can change all of the following EXCEPT one. Which CANNOT be changed by a force alone in the way described?

• A.the chemical identity of a substance
• B.the speed of a moving body
• C.the direction of motion
• D.the shape of a soft object

Answer: A. the chemical identity of a substance

NCERT fact (physics, chapter 'How Forces Affect Motion'): Forces change motion, shape or direction, not the chemical identity of matter. Why option A fits - Correct. Distractor analysis: option B) 'the speed of a moving body' is incorrect: A force can change speed; option C) 'the direction of motion' misses the point - A force can change direction of motion. Final answer - A) the chemical identity of a substance.

Q3. Which observation shows that force is a vector quantity?

• A.the effect of a force depends on its direction as well as its size
• B.force has only magnitude
• C.force never changes motion
• D.force is measured in kilograms

Answer: A. the effect of a force depends on its direction as well as its size

Which principle settles this? A quantity needing both magnitude and direction is a vector; force qualifies. Does that line up with one of the options? Yes - Correct. And the rest? option B) 'force has only magnitude' doesn't hold - If it had only magnitude it would be a scalar; it is a vector; option C) 'force never changes motion' misses the point - Force does change motion; this is unrelated to being a vector. Pick: A) the effect of a force depends on its direction as well as its size.