Chapter 8: Force and Laws of Motion Application Questions | science Class 9 CBSE

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Chapter 8: Force and Laws of Motion Application Questions | science Class 9 CBSE | ByteNotes.in

Application Question

Concept in a practical situation

Application

Question 1

Applied Concept

Q1. State Newton’s three laws of motion with examples.

1st Law: Object stays in rest/motion unless unbalanced force acts (e.g., coin flick).
2nd Law: F = ma; acceleration depends on mass and force (e.g., pushing a cart).
3rd Law: Every action has equal and opposite reaction (e.g., balloon release).
Laws explain all classical motion behaviors.
Foundation of mechanics.

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Application Question

Concept in a practical situation

Application

Question 2

Applied Concept

Q2. Define momentum and derive the relation F = ma.

Momentum p = mv.
Force = rate of change of momentum: F = (mv - mu)/t.
F = m(v - u)/t = ma if a = (v - u)/t.
Hence, F = ma.
This is Newton’s Second Law.

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Application Question

Concept in a practical situation

Application

Question 3

Applied Concept

Q3. Why do athletes bend knees while landing from a height?

Bending increases time of impact.
Reduces rate of change of momentum.
Thus, impact force decreases.
Prevents injury.
Same principle as pulling hands while catching.

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Application Question

Concept in a practical situation

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Question 4

Applied Concept

Q4. Why is it difficult to push a car than a cycle?

Car has greater mass.
More inertia resists motion.
Requires more force to change its state.
Cycle has less inertia → easier to push.
F = ma: more m → more F needed.

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Application Question

Concept in a practical situation

Application

Question 5

Applied Concept

Q5. A bullet of mass 20 g is fired with velocity 500 m/s. Find recoil velocity of 5 kg gun.

Using conservation of momentum:
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂.
Initially at rest → total momentum = 0.
0 = 0.02×500 + 5×v → v = -2 m/s.
Gun recoils with velocity 2 m/s (opposite direction).

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Application Question

Concept in a practical situation

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Question 6

Applied Concept

Q6. What is inertia? What are its types?

Inertia is the tendency to resist change in state.
Types: Inertia of rest (e.g., coin flick),
Inertia of motion (e.g., moving train lurch),
Inertia of direction (e.g., sudden turn in car).
Depends on mass of object.

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Chapter 8: Force and Laws of Motion | Application Questions

Q1. State Newton’s three laws of motion with examples.

Q2. Define momentum and derive the relation F = ma.

Q3. Why do athletes bend knees while landing from a height?

Q4. Why is it difficult to push a car than a cycle?

Q5. A bullet of mass 20 g is fired with velocity 500 m/s. Find recoil velocity of 5 kg gun.

Q6. What is inertia? What are its types?

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