- Push or pull that is exerted on an object
- Cannot be seen
- Its effect can be seen or felt
- Has magnitude and direction
- Is involved in many of our daily activities
Examples of activities that involve force
- Pushing a trolley
- Opening a door
- Opening the lid of a can
- Pulling a box
- Cycling
- Lifting a chair
Effects of force
- Can change the shape of object
Diagram 1 : A platicine is flattened
- Can change the size of an object
Diagram 2 : A can is crushed
- Can move a stationary object
Diagram 3 : A stationary ball moves when it is kicked
- A goalkeeper stops the ball
Diagram 4 : A goalkeeper stop the ball
- Can change the speed of a moving object
Diagram 5 : A ping-pong ball moves faster
- Can change the direction of moving object
Diagram 6 : A ping-pong ball changes its direction
Note : A force cannot change the mass of an object
Types of forces
1. Frictional force
- Occurs when two surfaces are in contact
- Always opposes the motion of the object
- Acts in the opposite direction to movement
- The direction of the force is parallel to the surface
- Can slow down or stop a moving object
2. Gravitational force
- Force that pulls all objects to the earth
- Causes all objects to fall towards the Earth
- Causes all objects to have weight
- Weight of an object is the pull of the force of gravity on it
3. Electrostatic force
- Force of attraction or repulsion between charged substances
- Enables charged substance to attract neutral substances such as small pieces of paper
- Substances with like charges repel each other
- Substances with unlike charges attract each other
4. Magnetic force
- Force of attraction exists between two unlike poles of magnets
- Force of repulsion exists between two like poles of magnets
- Force of attraction between the magnetic substances and the magnet
- Enables a magnet to attract magnetic substances like iron, nickel and cobalt
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