GCSE Edexcel Physics 2.2 - Forces

If there is no resultant force:
An object will continue moving at a constant velocity
Or remain at rest if stationary.

A moving object will continue moving at a constant velocity
A stationary object will remain stationary

Forces acting on an object are balanced
Resultant force is zero
Example of Newton's First Law

Velocity is changing!
So there is a resultant force.
Not Newton’s First law!

Acceleration is proportional to the resultant force
Acceleration is inversely proportional to the mass

Force (N) = mass (kg) x acceleration (m/s²)

If there is a resultant force, an object will accelerate (or decelerate)
The larger the resultant force, the larger the acceleration
The larger the mass, the smaller the acceleration

Force due to gravitational attraction (N)

Acceleration due to gravity (m/s²)
Gravitational field strength (N/kg)

Weight (N) = mass (kg) x gravitational field strength (N/kg)

Measure of the amount of matter (kg)

(Electronic) Balance

Weight

Attach object to newton meter
The reading is the weight (in Newtons)
Use W=mg to calculate the mass.

Weight is proportional to gravitational field strength
As gravitational field strength increases, weight increases.

When two bodies interact, the forces they exert on each other are equal and opposite

Two forces acting on different objects
Equal in magnitude but opposite in direction
Same type of force (push or pull)

In both forces are equal and opposite
1st Law: Both forces acting on the same object
3rd Law: Forces acting on different objects