Sci Chapter F1.

1. What is a forcce?

1.1. Forces are all around us.We need forces to hold things like books and close doors.

1.2. A force is a push or pull

1.3. We cannot see force but we can see the effects of forces.

1.4. A force can change the shape and size of an object, change the direction of a moving object and slow down or increase the speed of a moving object.

1.5. The SI unit of force isNewton ( N )

2. Force pressure and work

2.1. The most important forces are magnetic force, gravitational force and frictional force.

2.2. Frictional force occurs when two surfaces rub against each other.Friction opposes motion. The rougher the surface, the more the frictional force.Friction is used for walking , gripping things and many others.. Friction can be harmful. Friction can be reduced by lubricants, rollers, wheels and ball bearings.

2.3. Magnetic force is caused by two things attracting and repelling each other.Likes poles of a magnet repel each other while unlike poles attract each other.Magnetic force acts at a distance.Uses of magnets : Magnetic door catch,compass,Maglev train.

2.4. Gravitational force / weight is the force that is pulling you to the centre of the earth.It is also know as ghavity.weight is the measure of force acting on an object due to gravity.Mass and weight are different.

3. Pressure.

3.1. The amount of force applied per unit area. per unit area : 1 metre square.

3.2. The smaller the surface area, the more pressure.

3.3. The larger the surface area, the lesser the pressure.

4. How to measure pressure?

4.1. Pressure is force divided by area

4.2. The unit of pressure is N/unit2