General Science Physics - Mechanics

Force

A push, or a pull, that causes an object to undergo a change in speed, a change in direction, or a change in shape. Measured in newtons (N)

Balanced force

are equal in size and opposite in direction, giving a net force of zero. The object remains at rest or moves at constant velocity.

Unbalanced force

Forces that do not cancel, causing a change in motion (acceleration, deceleration, or change in direction).

Net Force (Resultant Force)

is the overall force acting on an object after all forces are combined.

Newton

The unit for force.

Mass

The amount of matter contained within an object. Measured in kilograms (kg). Mass does not change with location.

Weight

The force of gravity acting on an object’s mass. Measured in newtons (N). Weight = mass × gravitational field strength (10).

Gravity

a force that attracts objects with mass toward each other. On Earth, it causes objects to accelerate downward.

Normal Force

The support force exerted by a surface on an object, acting perpendicular (90°) to the surface.

Friction

A force that opposes motion between two surfaces in contact.

Air Resistance (Drag)

A frictional force that opposes motion when an object moves through air.

Applied Force

A force exerted on an object by a person or another object.

Thrust

A force that pushes an object forward, often produced by engines or explosions.

Newton’s First Law

An object will remain at rest or move at constant speed in one direction unless acted on by an unbalanced force.

Inertia

The tendency of an object to resist changes in its motion. Objects with more mass have more inertia.

Newton’s Second Law

An object will accelerate in the direction of an unbalanced force - Fₙₑₜ = ma.

Newton’s Third Law

For every action force, there is an equal and opposite reaction force acting on another object. These forces are never balanced.

Delta (Δ)

A symbol used in physics to show final – initial.

Distance

How far an object travels. Measured in metres (m).

Time

How long it takes to complete a motion. Measured in seconds (s).

Speed

How fast an object moves – rate of change in distance. Calculated by speed = distance ÷ time. Measured in metres per second (m s⁻¹).

Acceleration

The rate of change of speed in one direction. Changing speed or direction counts as acceleration. Measured in metres per second squared (m s⁻²).

Deceleration

The acceleration that decreases speed (negative acceleration).

Distance–Time Graph

A graph showing how distance changes with time. Gradient = speed, and a flat line = object at rest (not moving).

Speed–Time Graph

A graph showing how speed changes with time. Gradient = acceleration, and area under the graph = distance travelled.

Energy

Energy is the ability to do work. Measured in joules (J)

Joule

The unit of work and energy.

Gravitational potential energy

The energy stored in an object due to its height above Earth. Calculated using the formula.ΔEP= mgΔh. Unit is the joule (J)

Kinetic Energy

The energy of an object due to its motion. Calculated using the formula Ek=½mv2

Energy Transformation

When energy changes from one form to another (e.g. Ep to Ek).

Law of conservation of energy

states that energy cannot be created or destroyed, only transferred or transformed.

Work

The energy transferred when a force moves an object in the direction of the force. Formula - Work = force × distance (W = Fd)

Work done

Equal to the change in energy.

Power

The rate at which work is done or energy is transferred. Power = work ÷ time (P = W/t)

Watt (W)

The unit of power.