Forces

Scalars and vectors:

Vector quantities have a magnitude (size) and a direction. E.g. force, velocity, displacement, acceleration, momentum.

Scalar quantities only have a magnitude and no direction. E.g. speed, direction, temperature, time, mass.

Contact and non-contact forces:

A force is a push or pull on an object which is caused by an interaction with something. A contact force is when two objects have to be touching for a force to act.

A non-contact force is when two objects don't have to be touching for a force to act.

Gravity, mass and weight:

Gravity attracts all masses and makes all things fall towards the ground, it gives everything a weight. 

Mass is the quantity of matter that something contains and this is the same everywhere in the universe. Not a force, measured in kg.

Weight is the force acting on an object due to gravity, weight changes depending on how close you are to the centre of the gravitational field. Measured in newtons. Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg) 

Weight and mass are directly proportional.

Resultant forces:

Free body diagrams show all the forces acting on an object/system. A resultant force is the overall force on an object. So if a car has an acceleration force of 400N but an air resistnace force of 200N, the resutant force is 400-200=200N.

To make something move, a force is applied. In order for the force to be applied, there needs to be an energy source so the force does work to move the object by transferring energy from one store to another. Work done=energy transferred. Work done (J) = Force (N) x Distance (m). W=Fs.

Calculating forces:

You can find resultant forces using a scale drawing. Draw a line from the first force…