# Equations relating to mass, weight, density and forces and motion Forces
Balanced forces do not alter the velocity of a body. When forces are balanced an object will continue in a state of uniform motion.

#### Definitions

Mass is the property of a body which resists change in motion
Note the GCSE definition: Mass is the amount of matter a body contains is no longer satisfactory.

Weight is the force on an object due to gravity acting on its mass.

A Newton is the force which when applied to a mass of 1 kg produces an acceleration of 1 ms-2.

Connected Particles Questions using F=ma
Example: A 750kg car is pulling a 200Kg trailer. The Engine force = 12000N. Calculate the acceleration and tension. ### The most complicated type of vector questions

Example: A car of 800kg is parked on a slope at 30 degrees to the horizontal. Calculate the acceleration of the car down the slope assuming friction and air resistance is negligible. These three forces can be resolved into a vector triangle (although it may not seem obvious) by applying some basic angle in triangle rules.  