Let's analyze each question in detail:

Question 3

A horizontal force is applied to a body and is twice the force of gravity. What acceleration will the body experience?

Key Idea:

• Force $F = ma$, and the weight $mg$ represents the force of gravity.
• The horizontal force is $F = 2mg$.
• Using Newton's second law: $F = ma \implies a = \frac{F}{m}.$
• Substituting $F = 2mg$: $a = \frac{2mg}{m} = 2g.$

Correct Answer:

(2) $2g$

Question 4

Newton's Third Law states that for every action, there is an equal and opposite reaction. To whom does this law apply?

Options Analysis:

1. Two interacting bodies of any mass and shape: Correct, the law applies universally to all interacting bodies regardless of their size, mass, or form.
2. Only two interacting material points: Incorrect, as it is not limited to material points.
3. Inertial forces: Incorrect, as Newton's third law applies to action-reaction pairs, not inertial forces.

Correct Answer:

(1) Two interacting bodies of any mass and shape.

Question 5

A body is lifted upward with acceleration. Which statement about its weight is true?

Key Idea:

• Apparent weight $W_{\text{apparent}}$ is the normal force experienced by the object. When accelerating upward: $W_{\text{apparent}} = m(g + a).$
• If $a > 0$, $W_{\text{apparent}} > mg$ (weight appears greater than the gravitational force).

Options Analysis:

1. Weight equals zero: Incorrect, this would only occur in free fall ($a = -g$).
2. Weight is greater than the force of gravity: Correct, due to the upward acceleration adding to gravity.
3. Weight is less than the force of gravity: Incorrect, this would occur if accelerating downward.
4. Weight equals the force of gravity: Incorrect, this only occurs if there is no acceleration ($a = 0$).
5. None of the above: Incorrect, as (2) is true.

Correct Answer:

(2) Weight is greater than the force of gravity.

Final Answers:

• Question 3: (2) $2g$
• Question 4: (1) Two interacting bodies of any mass and shape.
• Question 5: (2) Weight is greater than the force of gravity.

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