BMST Newton's Laws of Motion 4 — Questions and Answers
Question 1: Inertia is defined as:
- The force that causes acceleration
- The tendency of an object to resist changes in its state of motion (Correct answer)
- The speed of an object in motion
- The friction between two surfaces
Correct answer: The tendency of an object to resist changes in its state of motion
Inertia is an object's resistance to changes in motion, and it is proportional to the object's mass.
Question 2: A car of mass 1,000 kg accelerates from rest to 20 m/s in 10 seconds. What is the net force on the car?
- 200 N
- 2,000 N (Correct answer)
- 20,000 N
- 100 N
Correct answer: 2,000 N
a = Δv/t = 20/10 = 2 m/s²; F = ma = 1000 × 2 = 2,000 N.
Question 3: If you exert a force on a skateboard and it accelerates at 2 m/s², but a heavier skateboard with the same force accelerates at 1 m/s², what does this tell you?
- Force and acceleration are unrelated
- Acceleration decreases as mass increases (Correct answer)
- Mass and acceleration are directly proportional
- The heavier board has more force acting on it
Correct answer: Acceleration decreases as mass increases
Newton's Second Law shows that for constant force, greater mass results in less acceleration (inverse relationship).
Question 4: Which best describes the action-reaction pair when a bat hits a baseball?
- The bat exerts force on the ball; the ball exerts an equal and opposite force on the bat (Correct answer)
- The bat exerts more force on the ball than the ball exerts on the bat
- Only the bat exerts force
- The ball exerts more force on the bat after the hit
Correct answer: The bat exerts force on the ball; the ball exerts an equal and opposite force on the bat
Newton's Third Law: the bat and ball exert equal and opposite forces on each other.
Question 5: A spacecraft traveling in deep space (no gravity, no air resistance) turns off its engines. What happens?
- It slows down gradually
- It stops immediately
- It continues at constant velocity (Correct answer)
- It accelerates due to momentum
Correct answer: It continues at constant velocity
With no net force, Newton's First Law says the spacecraft continues at constant velocity.
Question 6: A 2 kg book rests on a table. The normal force from the table on the book is approximately:
- 2 N
- 9.8 N
- 19.6 N (Correct answer)
- 4.9 N
Correct answer: 19.6 N
The normal force equals the weight: W = mg = 2 kg × 9.8 m/s² = 19.6 N.
Question 7: If you push two objects with the same force but one has more mass, which object has greater inertia?
- The lighter object
- The heavier object (Correct answer)
- Both have equal inertia
- Inertia doesn't depend on mass
Correct answer: The heavier object
Inertia is directly proportional to mass; the heavier object resists changes in motion more.
