Tahsili Physics 2 — Questions and Answers
Question 1: What is Newton's Third Law of Motion?
- An object at rest stays at rest
- F = ma
- For every action, there is an equal and opposite reaction (Correct answer)
- Energy cannot be created or destroyed
Correct answer: For every action, there is an equal and opposite reaction
Newton's Third Law states that when object A exerts a force on object B, object B simultaneously exerts an equal and opposite force on object A. These action-reaction pairs act on different objects.
Question 2: A projectile is launched at 45° with an initial velocity of 20 m/s. What is the horizontal component of velocity?
- 20 m/s
- 10 m/s
- 20/√2 ≈ 14.14 m/s (Correct answer)
- 10√2 m/s
Correct answer: 20/√2 ≈ 14.14 m/s
Horizontal component: vₓ = v₀cos(45°) = 20 × cos(45°) = 20 × (√2/2) = 20/√2 ≈ 14.14 m/s. At 45°, both horizontal and vertical components are equal.
Question 3: What is the total resistance of three resistors (2Ω, 3Ω, 6Ω) connected in parallel?
- 11 Ω
- 1 Ω (Correct answer)
- 0.5 Ω
- 6 Ω
Correct answer: 1 Ω
For parallel: 1/R = 1/2 + 1/3 + 1/6 = 3/6 + 2/6 + 1/6 = 6/6 = 1. Therefore R = 1Ω. Parallel resistance is always less than the smallest individual resistor.
Question 4: What happens to the gravitational force between two objects if the distance between them is doubled?
- It doubles
- It halves
- It becomes one-quarter (Correct answer)
- It remains the same
Correct answer: It becomes one-quarter
Gravitational force follows the inverse square law: F = Gm₁m₂/r². If r doubles (2r), F = Gm₁m₂/(2r)² = Gm₁m₂/4r² = F/4. The force becomes one-quarter of the original.
Question 5: What is the principle of conservation of momentum?
- Momentum always increases in collisions
- In an isolated system, total momentum before a collision equals total momentum after (Correct answer)
- Momentum is only conserved in elastic collisions
- Heavier objects always have more momentum
Correct answer: In an isolated system, total momentum before a collision equals total momentum after
Conservation of momentum states: in an isolated system (no external forces), total momentum is constant. m₁v₁ + m₂v₂ = m₁v₁' + m₂v₂'. This applies to ALL collisions (elastic and inelastic) and is fundamental to the Tahsili physics section.
Question 6: An object has a mass of 2 kg and velocity of 3 m/s. What is its kinetic energy?
- 6 J
- 9 J (Correct answer)
- 12 J
- 18 J
Correct answer: 9 J
KE = ½mv² = ½ × 2 × 3² = ½ × 2 × 9 = 9 J. Kinetic energy depends on the square of velocity, so doubling speed quadruples kinetic energy.
Tahsili Physics 2
What is Newton's Third Law of Motion?