10 questions · Form 4 Physics Bab 2: Force and Motion I
Why does a passenger jerk forward when a fast-moving bus suddenly applies the brakes?
Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.
1. Why does a passenger jerk forward when a fast-moving bus suddenly applies the brakes?
Answer: B
By Newton's First Law, the passenger's body tends to maintain its state of forward motion due to inertia.
2. A stone is thrown vertically upwards with an initial velocity of 15 m s⁻¹. Assuming g = 9.81 m s⁻² and neglecting air resistance, what is its velocity at the maximum height?
Answer: C
At maximum height, an object momentarily comes to a complete stop, so its velocity v = 0 m s⁻¹.
3. According to Newton's Second Law of Motion, acceleration is:
Answer: A
From F = ma => a = Fm. Thus, a ∝ F and a ∝ 1m.
4. Impulse is defined as the change in momentum. Its SI unit is equivalent to:
Answer: B
Impulse J = F × t (Newton-seconds, N s), which is equivalent to kg m s⁻¹.
5. What is the momentum of a 1200 kg car traveling at a constant velocity of 15 m s⁻¹?
Answer: C
Momentum p = mv = 1200 kg × 15 m s⁻¹ = 18,000 kg m s⁻¹.
6. The inertia of an object depends EXCLUSIVELY on its:
Answer: D
Mass is the sole measure of inertia. Larger mass means greater inertia.
7. A gun fires a bullet forward. According to the Principle of Conservation of Momentum, why does the gun recoil backward?
Answer: C
Initial momentum is 0. Backward recoil momentum (-m_gun × v_gun) balances forward bullet momentum (m_bullet × v_bullet) so total momentum stays 0.
8. An object in free fall near Earth's surface accelerates at approximately 9.81 m s⁻². This means that during every second of fall:
Answer: B
Acceleration of 9.81 m s⁻² means velocity increases by 9.81 m s⁻¹ every second.
9. A soccer player kicks a 0.5 kg stationary ball, giving it a speed of 20 m s⁻¹. If the foot stays in contact with the ball for 0.05 s, calculate the average force exerted on the ball.
Answer: C
F = mv - mut = 0.5 × 20 - 00.05 = 100.05 = 200 N.
10. What is the physical quantity defined as the rate of change of displacement?
Answer: B
Velocity is defined as the rate of change of displacement (v = st in a specific direction).