Work — Science definition
Defined in 2 courses:
- Energy transferred by a force acting through a displacement. (Physical Science: Matter, Forces & Energy)
- The energy transferred to an object when a force acts on it through a displacement: W = Fd·cosθ, measured in joules (J). (Physics & Environmental Science)
Where it is taught
- Work: Transferring Energy with a Force — Work & Machines, Physical Science: Matter, Forces & Energy, Grade 8
- Work & Power — Work, Energy & Momentum, Physics & Environmental Science, Grade 12
In use
In science, work is energy transferred by a force acting through a displacement.
Work: Transferring Energy with a Force
In everyday speech 'work' means almost any effort, but in physics it has a sharp, specific meaning: work is the energy a force transfers to an object as that object moves.
Work & Power
Questions using work
Problem 1
A 5 N force moves a cart 4 m in the same direction. Find its work.
Answer and explanation
20 J
5 × 4 = 20.
Problem 2
You push a wall that remains still. Mechanical work on the wall is…
- zero
- equal to your mass
- always 100 J
- infinite
Answer and explanation
zero
The wall has no displacement.
Problem 3
Why can you feel tired while holding a heavy bag still although no mechanical work is done on the stationary bag?
Answer and explanation
Your body uses chemical energy, but the bag has no displacement. The objects and energy transfers being considered differ.
Problem 4
A horizontal 15 N force moves a box 4 m in the same direction. Find the work; compare with holding it still. Explain the reasoning in your own words.
Answer and explanation
60 J while moving; 0 J on the stationary box by the supporting force.
Use W=Fd=15×4=60 J.
With zero displacement, mechanical work on the stationary box is zero.
Response criteria
- Use the stated conditions.
- Show the evidence or calculation.
- Explain the conclusion and any stated limitation.