FORCE AND PRESSURE

1. Magnetic force

1.1. Some matellic materials are magnetic but some are not

1.2. Magnetic forces are often very strong compared to other forces. E.g. magnets are used to lock doors, gates etc.

1.3. Magnetic force can also be used to push and pull objects.

2. WHAT IS A FORCE?

2.1. force is a push or pull

2.2. examples of forces: bouncing a ball,closing the door,etc.

3. WHAT ARE THE EFFECTS OF FORCES?

3.1. forces cannot be seen,only the effect of forces can be seen

3.2. force can change the shape of an object

3.2.1. example: when we press a platicine,it will flatten

3.3. force can change the speed of an object

3.3.1. example: when we push a moving car,the speed will increase

3.4. force can change the direction of an object

3.4.1. when we play tennis,we hit the moving ball back to the opponent's side

3.5. force can start a moving object

3.5.1. example: When we spin a wheel, it will start moving

3.6. force can stop a moving object

3.6.1. example: If we step on a moving object,it will stop moving

4. HOW CAN WE MEASURE FORCE?

4.1. We use force meters-spring balance

4.1.1. 2 types of spring balance

4.1.1.1. extension spring balance

4.1.1.1.1. The spring stretches when a force pulls on it. The greater the force,the longer the spring stretch

4.1.1.2. compression spring balance

4.1.1.2.1. The spring get compressed when a force acts upon it.

5. TYPES OF FORCES

5.1. Frictional force

5.1.1. Frictional force is a force that is created whenever 2 surfaces move or try to move across each other. ( the resistance )

5.1.2. HOW TO REDUCE FRICTION?

5.1.2.1. Frictional force can be reduced using a range of lubricants

5.1.2.1.1. example:oil,grease

5.1.2.1.2. This is because lubricants tend to make the contact smoother thus reducing the amount of frictional force.

5.1.3. others:

5.1.3.1. In some instances, frictional force is not only undesirable but also dangerous. When 2 rough surfaces are rubbed together, heat is usually generated. If this occurs with something flammable, it could result in a fire/ explosion

5.1.3.2. New node

5.2. Gravitational force

5.2.1. It is NOT a force of contact

5.3. Gravitational force can be good or bad.

5.3.1. Good in a way that it keeps us on the ground

5.3.2. Bad is that if there is a hole well…we would fall.

6. WHAT IS PRESSURE?

6.1. Pressure is the amount of force that is exerted perpendicularly per unit area.

6.2. If we apply more force, the amount of

6.3. pressure will be more. Similarly, if we apply lesser

6.4. force, the amount of pressure will be lesser.

6.5. There are different types of pressure. They are air pressure, water pressure and many more.

6.6. The SI unit area for pressure is Pascal(Pa). The formula for pressure is force divided by area.

7. HOW CAN WE INCREASE PRESSSURE?

7.1. Pressure is given by the equation force divided by area. To increase the pressure for a solid or a liquid, we can just push harder on it. For gas, we can increase the pressure by either increasing the amount of gas, increasing the temperature or by decreasing the volume of the container.

8. HOW CAN WE DECREASE PRESSURE?

8.1. To decrease pressure, we can decrease the amount of force applied and we can make the area bigger.

9. CALCULATING PRESSURE

9.1. pressure=force/area

9.2. Example:A lump of cheese of weight 20N stands on a table. It is a cubic lump with an area of 10cm2. What pressure does it exert on the table?

9.3. Answer:20N/10cm2=2N/cm2

9.4. Example:The surface area of an elephants foot is 100cm squared and force is 30,000n. What is the pressure on the ground?