Hooke’s Law + Terminal Velocity

Weight

The force acting on an object due to gravity

Mass

The amount of matter in an object

Gravitational field strength

The force per unit mass acting on an object

Weight equation

Weight equals mass times gravitational field strength

W = m × g

Equation linking weight, mass and gravitational field strength

Units of weight

Newtons (N)

Units of mass

Kilograms (kg)

Units of gravitational field strength

N/kg

Forces on a falling object

Weight acts downward and air resistance acts upward

Air resistance

A force that opposes motion through air

Resultant force

The overall force acting on an object

Acceleration of a falling object

Occurs when weight is greater than air resistance

Terminal velocity

The constant maximum speed reached by a falling object

Why terminal velocity is reached

Air resistance increases until it equals weight

Forces at terminal velocity

Weight equals air resistance

Resultant force at terminal velocity

Zero

Motion at terminal velocity

Object moves at constant speed

Hooke’s Law

Extension is proportional to force

Hooke’s Law equation

Force equals spring constant times extension

F = k × e

Equation for Hooke’s Law

Spring constant

A measure of how stiff a spring is

Units of spring constant

N/m

Force-extension graph

Graph showing how extension varies with force

Linear region

Straight-line part of a force-extension graph

Meaning of linear region

Hooke’s Law applies

Limit of proportionality

Point where the graph stops being straight

Elastic behaviour

Ability of a material to return to its original shape after deformation

Elastic deformation

Deformation that is reversible

Inelastic deformation

Deformation that is permanent

Hooke’s Law practical

Investigates how extension varies with applied force

Equipment for Hooke’s Law practical

Spring, ruler, clamp stand and masses

Method of Hooke’s Law practical

Add masses and measure extension

Conclusion of Hooke’s Law practical

Extension increases proportionally with force in the linear region