1. What is Work Done by Normal Force?

Definition: The work done by the normal force is always zero when an object moves along a surface.

Explanation: Since the normal force acts perpendicular to the direction of motion, it does no work on the object.

2. The Physics Behind the Formula

The formula is:

Where:

• \( W_n \) — Work done by normal force (Joules, J)

Key Concept: Work is only done when a force has a component in the direction of displacement. The normal force is always perpendicular to displacement.

3. When Does This Apply?

Details: This principle applies in all cases where:

• An object moves along a surface
• The normal force is perpendicular to the direction of motion
• There is no vertical displacement

4. Practical Implications

Examples:

• A book sliding on a table - normal force does no work
• A car driving on a flat road - normal force from road does no work
• A person walking - normal force from ground does no work

5. Frequently Asked Questions (FAQ)

Q1: Why is the work done by normal force zero?
A: Because work = force × displacement × cos(θ), and θ = 90° for normal force, making cos(90°) = 0.

Q2: Are there any exceptions?
A: Only if the surface itself is moving vertically (like an elevator), then the normal force might do work.

Q3: Does friction affect this?
A: No, the normal force's work is independent of friction, though friction does do work (negative work).

Q4: How is this different from gravitational work?
A: Gravity can do work when there's vertical displacement, unlike the normal force in typical horizontal motion.

Q5: Is energy conserved when normal force does no work?
A: Yes, since no energy is transferred by the normal force, conservation laws still apply to the system.