Physics Study Guide: Forces, Equilibrium, and Newton's Laws

Q2. A student makes the following statement: "An object cannot be in mechanical equilibrium when only a single force is acting on it." Do you agree or disagree with this statement? Explain your answer.

Background

Topic: Mechanical Equilibrium and Net Force

This question tests your understanding of mechanical equilibrium, which occurs when the net force on an object is zero. It asks you to reason about whether a single force can ever result in equilibrium.

Key Terms and Formulas:

• Mechanical Equilibrium: A state where the net force ($F_{\text{net}}$) on an object is zero.

• Net Force: The vector sum of all forces acting on an object.

• Static Equilibrium: Object at rest ($v = 0$).

• Dynamic Equilibrium: Object moving at constant velocity ($v = \text{constant}$).

• $F_{\text{net}} = 0$

Step-by-Step Guidance

1. Recall the definition of mechanical equilibrium: it requires that the net force on the object is zero ($F_{\text{net}} = 0$).

2. Consider what happens if only one force acts on an object. Is it possible for the net force to be zero in this case?

3. Think about the vector sum of forces: with only one force, the net force is equal to that force, so $F_{\text{net}} \neq 0$ unless the force itself is zero.

4. Mechanical equilibrium can be static (at rest) or dynamic (constant velocity), but in both cases, $F_{\text{net}} = 0$ is required.

Try solving on your own before revealing the answer!

Final Answer:

You should agree with the statement. Mechanical equilibrium occurs only when the net force is zero. If only one force acts on an object, the net force cannot be zero (unless the force itself is zero), so equilibrium is not possible.

This is why objects in equilibrium must have at least two forces acting in opposite directions, balancing each other out.