Hydraulic Press: Audit the Work

Check the energy budget instead of calling a machine magic.

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For a constant force along the motion, work = force x distance. Use meters and newtons for joules. An ideal press trades distance for force; a real press delivers less useful work because of losses. Use diagrams and calculations only; never build or operate a press for this activity.

Worked example

An ideal input of 6 N through 0.08 m transfers 0.48 J. An output of 24 N through 0.02 m also transfers 0.48 J.

Input work is 6 newtons times 0.08 meters, giving 0.48 joules. Output work is 24 newtons times 0.02 meters, also 0.48 joules. Equal bars represent equal work, not equal forces.

Would you believe it?

Many powered hydraulic machines use a motor-driven pump to supply energy. A large output force is not free energy; force and travel must both be counted.

OpenStax: hydraulic work and energy

Question 1 What is the input work, 6 N x 0.08 m? 6.08 J 0.48 J 48 J

Question 2 What is the output work, 24 N x 0.02 m? 0.48 J 12 J 24.02 J

Question 3 What does this ideal comparison show? Four times as much output work No input energy is needed Equal input and output work

Question 4 A real output is 0.36 J from a 0.48 J input. Where can the rest go? It becomes negative energy Heating and other losses It disappears from the universe

Question 5 Which claim needs rejecting? More force always means more work Work depends on distance too A powered pump supplies energy

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