FORMULA SHELF
7 of 370
The arithmetic behind the work: what to measure, what to type in, and what the answer comes out as. Every formula says what the symbols mean and gives a worked example, so you can check it against a job you have already done.
SHELVES
Workshop
1 formulas
Friction and heat are the losses. A lower efficiency means more fuel, more electricity and more heat to shift away.
A 1 kW motor driving a 400 W pump is 40% efficient, which means something is rubbing.
Physics
4 formulas
A lever, a block and tackle, a ramp, a screw jack. You trade distance for force, and no machine beats 100% efficiency. A ramp 4 m long and 1 m high has a theoretical advantage of 4.
A block and tackle with 4 supporting parts needs a quarter of the force.
Convenience only. Double-check the result against the worked example or a second method before you use it.
The jack, the brake press, the loader bucket and the post hole rammers. A 10 cm piston moved with 100 N will lift 1,000 kg on a 1 m piston.
A 100 N push on a 10 cm2 piston lifts 1,000 kg on a 1,000 cm2 piston.
Ramps, loading ramps, the screw jack, the post hole auger and the cider press. Work in always equals work out, so a gentle ramp just means more walking.
A 2 m ramp at 500 mm high gives an advantage of 4.
The whole of the spanner, the jack, the pump handle and the gate hinge. Torque depends on where you put your hand, not on how hard you pull. A 100 N push at 0.3 m gives 30 N m.
A 300 N pull on a 0.4 m spanner gives 120 N m.
Convenience only. Double-check the result against the worked example or a second method before you use it.
Trigonometry
1 formulas
Roof pitches, ramps, braces and setting out any right-angle triangle.
A 10 m rafter at 30 degrees rises 5 m.
Surveying
1 formulas
Placing a contour line between two surveyed levels on a plan.
Levels 8.2 and 9.0 m at 10 m apart: the 8.5 m contour is 3.75 m from the low point.
SOURCES & PROVENANCE
1 listed
This page is an AI-organised index. The label means the grouping and cross-links were compiled with AI; the information itself comes from the public-domain books, reports and manuals listed below. Open any source to read the local copy or follow the link to the original publication.