Scalars, vectors and types of force

Scalar quantity

quantity that has a magnitude (size) only

Examples of scalar quantities

Speed, temperature, mass, energy, distance, density

Vector quantity

quantity that has a magnitude and direction

Examples of vector quantities

Velocity, force, displacement, acceleration, momentum

Representing vector quantities

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

Contact forces

Forces between two objects that are physically touching each other

Examples of contact forces

friction, air resistance, tension

Non-contact forces

Forces between two objects that are not physically touching each other

Examples of non-contact forces

gravitational force, electrostatic force, magnetic force

Free body diagram

A diagram showing all the forces acting on an object

Friction

contact force that always opposes the motion of an object