Define work done.
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Work done is the product of force and distance moved in the direction of the force.
Work
A student pushes a trolley with a constant horizontal force across a laboratory floor. Explain why the work done by the student equals the energy transferred to the trolley and its surroundings.
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The student exerts a force on the trolley over a distance in the direction of the force; therefore work is done on the trolley. Work done is equal to energy transferred; so energy is transferred from the chemical store of the student to the kinetic store of the trolley and the thermal store of the surroundings (due to friction).
A crane lifts a steel beam weighing 6000 N through a vertical height of 15 m. Calculate the work done by the crane.
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Finding the work done Equation used $$W=F d$$ Given $$F=6000 \text{N}$$ $$d=15 \text{m}$$ Substitution $$W=6000\times 15$$ $$W=90 000 \text{J}$$ Answer $$W=90 000 \text{J} (90 \text{kJ})$$
A horizontal force does 3600 J of work on a crate, moving it 24 m across a warehouse floor. The force is then doubled while the crate is moved a further 24 m. State and explain what happens to the work done in the second 24 m compared with the first 24 m.
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The work done in the second 24 m is double the work done in the first 24 m. Because $W=Fd$, work done is directly proportional to force when distance is constant. The distance is the same (24 m) in both cases; therefore doubling the force doubles the work done. The work done in the second stage is $2\times 3600=7200$ J.