Physics - Mechanics

Topic 2

Acceleration

Change in velocity divided by time taken. Measured in m/s². A vector quantity.

Balance

A device for measuring the mass or weight of an object.

Deceleration

Negative acceleration; slowing down.

Displacement

Distance moved in a given direction. Measured in metres. A vector quantity.

Distance

Total distance travelled by an object. Measured in metres. A scalar quantity.

Drag

Resistance to motion when an object moves through a fluid, such as air or water.

Force

A push or pull exerted by one object on another. Can change velocity, direction, shape or transfer energy. Measured in Newtons (N).

Free fall

Downward motion under gravity, usually ignoring air resistance.

Friction

A force between surfaces that acts against motion. Can be static or dynamic.

Gradient

The slope of a graph, calculated using rise ÷ run.

Gravitational field

A region around an object with mass where gravitational forces act. Earth's gravitational field strength is about 10 N/kg.

Linear motion

Motion where acceleration is constant.

Mass

The amount of substance in an object. Measured in kilograms (kg).

Newton's First Law of Motion

An object stays at rest or moves at constant velocity in a straight line unless an external resultant force acts on it.

Newton's Second Law of Motion

The resultant force equals mass multiplied by acceleration: F = ma.

Newton's Third Law of Motion

When object A exerts a force on object B, object B exerts an equal and opposite force on object A.

Non-linear motion

Motion where acceleration changes.

Normal reaction force

A force acting perpendicular to a surface on an object touching it. On a flat surface, it is equal and opposite to weight if there are no other vertical forces.

Rest (at rest)

Not moving. An object at rest has zero velocity.

Resultant force

The single force that represents the vector sum of all forces acting on an object.

Scalar quantity

A quantity with magnitude and a unit, but no direction. Examples include speed, distance, energy and mass.

Speed

Distance travelled divided by time taken. Measured in m/s. A scalar quantity.

Terminal velocity

Constant velocity reached when forces are balanced and acceleration is zero, such as when a skydiver's weight equals air resistance.

Thrust / engine force

A force produced by an engine that causes motion. Measured in Newtons (N).

Upthrust

An upward force exerted by a fluid (liquid or gas) on an object. Similar to buoyancy.

Vector quantity

A quantity with magnitude, a unit and a direction. Examples include velocity, displacement, force and acceleration.

Velocity

Displacement divided by time taken. Measured in m/s. A vector quantity.

Weight

The force exerted on an object by gravity. Measured in Newtons (N). Calculated using W = mg.