Scalars, Vectors and types of force

Scalar quantity

A quantity that has a magnitude (size) only

Examples of scalar quantities

Speed, temperature, mass, energy, distance, density

Vector quantity

A quantity that has a magnitude and an associated direction

Examples of vector quantities

Velocity, force, displacement, acceleration, momentum

Representing vector quantities

Vector are represented by an arrow to indicate its size and direction

Contact forces

Forces that act between two objects that are physically touching each other

Examples of contact forces

friction, air resistance, tension, normal contact (reaction) force

Non-contact forces

Forces that act between two objects that are not physically touching each other

Examples of non-contact forces

gravitational force, electrostatic force and magnetic force

Resultant force

A single force that has the same effect as the original forces on an object acting together

Components of a force

A single force can be resolved into two components acting at right angles to each other and have the same effect as the single force

Free body diagram

A diagram showing all the forces acting on an object