This is the amount of material that makes up a body.

The unit of mass is the KILOGRAM.

The mass of a body determines its reluctance to accelerate when a force is applied to it.

The WEIGHT of a body depends upon the force of gravity and varies from place to place.

In outer space a body can weigh nothing.

It still needs the same amount of force to accelerate it as it would on the earth.

A body left to itself will remain motionless.

If it is already moving then it will continue to move in a straight line at a constant velocity.

Anything which changes these conditions is a force.

Force is measured in NEWTONS.
1 Newton is the force required to produce an acceleration of 1 metre per second per second (m/s²) in a mass of 1 kilogram.

F = mass x acceleration.  F=ma

When a force is applied to a body, the body will move (if free to do so).

It will move in the direction of the force.

The force has done WORK on the body.

Work = force x distance moved in the direction of the force.

The unit of work is the JOULE.

1 Joule is the work done when a force of 1 Newton moves an object a distance of 1 Metre.