Grade 9 Forces
1. What is a Force?
A force is a push or pull that acts on an object.
👉 Forces can change how objects move or look.
2. Effects of Forces
A force can:
Start moving a stationary object
Speed up an object (accelerate)
Slow down an object (decelerate)
Change the direction of movement
Change the shape of an object (deformation)
Cause an object to rotate (spin/turn)
👉 Even if you can’t see a force, you can stil observe its effects.
3. Unit and measurement of Force
The unit of force is the Newton (N)
Named after Sir Isaac Newton
Measuring Force:
Measured using a spring balance (Newton meter)
4. Forces Work in Pairs
Forces will always act in pairs.
👉 This is known as Newton’s Third Law (For every action, there is an equal and opposite
reaction)
Example:
If you push a wall, the wall pushes back on you.
5. Balanced vs Unbalanced Forces
✅Balanced Forces:
Equal in size
Opposite in direction
Net force = 0 N
Object stays still or moves at a constant speed
❌Unbalanced Forces:
Not equal
≠
Net force 0 N
Causes movement or change in motion
1. What is a Force?
A force is a push or pull that acts on an object.
👉 Forces can change how objects move or look.
2. Effects of Forces
A force can:
Start moving a stationary object
Speed up an object (accelerate)
Slow down an object (decelerate)
Change the direction of movement
Change the shape of an object (deformation)
Cause an object to rotate (spin/turn)
👉 Even if you can’t see a force, you can stil observe its effects.
3. Unit and measurement of Force
The unit of force is the Newton (N)
Named after Sir Isaac Newton
Measuring Force:
Measured using a spring balance (Newton meter)
4. Forces Work in Pairs
Forces will always act in pairs.
👉 This is known as Newton’s Third Law (For every action, there is an equal and opposite
reaction)
Example:
If you push a wall, the wall pushes back on you.
5. Balanced vs Unbalanced Forces
✅Balanced Forces:
Equal in size
Opposite in direction
Net force = 0 N
Object stays still or moves at a constant speed
❌Unbalanced Forces:
Not equal
≠
Net force 0 N
Causes movement or change in motion
