Notes

Learning Points
Summary of learning points:
1. Force
is a pull or a push.
We cannot see a force but we can observe the effects of forces.

2. Effects of forces
A force can cause an object at rest to start moving.
A force can cause a moving object to speed up, slow down or change its direction of motion.
A force can stop a moving object.
A force can change the shape of an object.

3. Frictional Force
Friction is a force between two surfaces, which resists the motion of an object.
Friction is affected by two factors:
Weight of the object and
The type of surface the object is in contact with
It gives us a grip on things. It prevents us from slipping. The grooves on the tyres of a vehicle helps help the vehicle to stay on the road and prevent it from skidding under wet and slippery conditions.Friction helps to stop or slow down a moving object.
Friction causes objects to: Overheat, Slow down, Wear out

4. Gravitational Force
It is the force that pulls everything down towards the Earth.
Gravity is a force that acts at a distance.
It makes an object move without actually touching it.
Without gravity, we would floating in the air.
The amount of gravity acting on an object depends on the distance the object is from the Earth.
The further an object is from the Earth, the less the pull of gravity.
All things on Earth have weight. The gravitational force between things and the Earth gives things weight.
A spring stretches when something is hung from it. The weight of the object causes it to stretch.Spring balances are used to measure weight.
Weight is a force. It is different at different places. An object weighs about one-sixth of what is weighs on Earth when it is on the Moon.

As an object falls through air, it usually encounters some degree of air resistance.Air resistance works in the opposite direction of gravity. (upwards vs downwards).To make an object drop slower, the amount of air resistance needs to be increased. In this case, this can be done by increase the surface area of the plastic sheet.

5. Elastic Spring Force
When a spring is pulled, a force that caused the spring to stretch is applied
The larger the force acting on a spring, the longer the spring stretches.
Materials that are elastic have the ability to return to their original shapes when a force is applied to them is removed.
The force that springs exert on objects that compress or stretch them is known as elastic spring force.

6. Magnetic Force
Forces of attraction (pull)When placed close to one another, A pair of magnets with unlike poles attract one another.
Forces of repulsion (push)When placed close to one another,A pair of magnets with like poles repel one another.