Grade 12

Strength of materials.

Simple problems. Hooke's law, stress and strain. Young's modulus. Tension and compression. Elastic limit. Ultimate strength. Factors of safety.

Friction.

Conditions affecting friction. Lubrication. Conditions should include types of materials, their surface finish and wetness or dryness.

Limiting friction. Coefficients of friction.

Work.

Work done by constant and by varying force; graphical representation of and calculations thereon. Energy, potential and kinetic. Conservation of energy and conversion into work, work done in rotation. Torque.

Machines.

Simple single-string pulley systems. Simple and differential wheel and axle. Weston pulley block. Screw jack. Worm (single start thread and wheel). Gear and belt drives. Velocity ratio, mechanical advantage and efficiency.

Power.

Simple treatment of steam and internal combustion engines. Indicators diagrams.Indicated mean effective pressure. Indicated and brake horsepower. Methods of measurement of power. Rope brake and Prony brake. Hydraulic power (as given by the product of constant pressure and rate of volume change). Mechanical efficiency. Relationship between rev/min and working strokes per minute in double-acting steam engines and in two and four-stroke internal combustion engines. The oscillating cylinder