Mechanical Comprehension

Mechanical advantage of a lever

Length of effort arm ÷ Length of load arm

First-class lever

Fulcrum is between the effort and the load (example: seesaw)

Second-class lever

Load is between the fulcrum and the effort (example: wheelbarrow)

Third-class lever

Effort is between the fulcrum and the load (example: tweezers)

Pulley mechanical advantage

Roughly equal to the number of supporting strands of rope

Inclined plane mechanical advantage

Length of the slope ÷ Height

Wheel and axle

Mechanical advantage = radius of wheel ÷ radius of axle

Gear ratio (basic)

If one gear has twice as many teeth, the other turns twice as fast with half the torque

Gears that mesh

They turn in opposite directions

Friction

Force that opposes motion between surfaces

Center of gravity

The point where the object’s weight seems to act. Lower = more stable.

Pressure

Force ÷ Area. Smaller area means higher pressure for the same force.

Pascal’s principle

Pressure applied to a confined fluid is transmitted equally in all directions

Bernoulli’s principle (simple)

Faster-moving fluid has lower pressure

Torque

Force × perpendicular distance from the pivot point. Causes rotation.

Mechanical advantage greater than 1

The machine multiplies force (but you usually move a greater distance)

Efficiency

(Work output ÷ Work input) × 100%. Always less than 100% because of friction.

Hydraulics basic idea

Force is multiplied by the ratio of the piston areas

Hooke’s law (springs)

Force is proportional to how much the spring is stretched or compressed

Energy conservation (no friction)

Total mechanical energy stays the same; kinetic and potential trade places