01Why this matters
Pushing something is not enough to calculate work: how far it moves, and in what direction, also matter.
02See it
03Understand it
Work is energy transferred by a force acting through a displacement.
For a constant force parallel to displacement, W = Fd. The SI unit is the joule, equal to a newton metre. A force in the direction of displacement does positive work; one opposing displacement does negative work. A force perpendicular to displacement does no work in this simple mechanical definition.
04Guided example
A constant 15 N force moves a box 4 m in the force’s direction. Find the work done by that force.
- The force and displacement are parallel, so use W = Fd.
- Substitute F = 15 N and d = 4 m.
- W = 15 × 4 = 60 J. This is the energy transferred by this force.
05Try it
06Practise it
07Use it in the real world
Lifting an object slowly transfers energy to its gravitational store. Holding it still can feel tiring, but there is no mechanical work on the stationary object because its displacement is zero.
Go a little deeper
The general constant-force formula is W = Fd cos θ, where θ is the angle between force and displacement. The dot product handles this in vector notation.
08Quick check
09Summary
Work is energy transferred by a force acting through a displacement. W = 15 × 4 = 60 J. This is the energy transferred by this force.
Before moving on, explain the worked example in your own words. Use the hint on any question you want to revisit.
10Key idea
W = Fd (parallel force)
W: work in J; F: constant force in N; d: displacement in m.
F = W/d; d = W/F for non-zero divisors
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