Work Means Move

Why it matters

Hold a heavy bucket perfectly still for five minutes. Your arms burn, your brow sweats — and physics coldly scores it: zero work. Physics has its own definition, and it involves moving.

The idea in plain words

Work's strict definition — no trigonometry needed. Tap each term.

W = F × d

Lift a 5 kg bag 2 m up (g = 10). Work done?

100 J

• joule (J): W — work — energy transferred by the force
• newton (N): F — the applied force
• metre (m): d — distance moved ALONG the force's direction — pull sideways and this is zero
• F = mg = 50 N, and the bag moves 2 m along the lift
• W = 50 × 2

Predict first

You push a wall with all your strength. It doesn't move. Work done on the wall = ?

W = F × d, and d = 0. Your muscles did INTERNAL work (that's the tiredness), but the wall received none.

• zero — force without displacement is not work — correct
• a lot — you're exhausted!
• depends on the wall

What you do

Drag the crate and watch work being counted — then find the pull that does no work at all.

Check yourself

1 joule = …

J = N × m. (Lifting 1 kg by 1 m is about 10 J — g does the conversion.)

You lift a 20 N bucket onto a shelf 1.5 m up. Work done on the bucket?

W = F × d = 20 × 1.5 = 30 J — force times the distance moved along it.

Work is done ON an object when…

Force AND motion together — either alone scores zero.

• 1 newton moving something 1 metre — correct
• 1 newton for 1 second
• 1 kg lifted 1 metre
• 30 J — correct
• 21.5 J
• 300 J
• a force moves it through a distance — correct
• you think hard about it
• it is merely heavy