Forces, Equilibrium, and Free-Body Diagrams – Step-by-Step Physics Guidance

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 the conditions required for mechanical equilibrium, specifically the relationship between the number of forces acting on an object and whether it can be in equilibrium.

Key Terms and Formulas:

• Mechanical Equilibrium: A state in which the net force on an object is zero, so the object is either at rest (static equilibrium) or moving at constant velocity (dynamic equilibrium).

• Net Force ($F_{\text{net}}$): The vector sum of all forces acting on an object.

Step-by-Step Guidance

1. Recall the definition of mechanical equilibrium: an object is in equilibrium if $F_{\text{net}} = 0$.

2. Think about what it means for only a single force to act on an object. If there is only one force, can the net force be zero?

3. Consider Newton's First Law: an object will remain at rest or move at constant velocity unless acted upon by a net (unbalanced) force.

4. Ask yourself: If there is only one force, is there any other force to balance it out? What would happen to the object's motion?

Try solving on your own before revealing the answer!

Final Answer:

You should agree with the statement. Mechanical equilibrium requires $F_{\text{net}} = 0$. If only one force acts, the net force cannot be zero, so the object cannot be in equilibrium. There must be at least two forces that balance each other for equilibrium.