Force and Pressure

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Force and Pressure by Mind Map: Force and Pressure

1. What is a Force?

1.1. A force is a PUSH or a PULL.

2. Effects:

2.1. - Change the speed of a moving object, either slowing it down or increasing its speed.

2.2. - Start an object or stop a moving object

2.3. - Change the shape or size of a moving object

2.4. - Change the direction of a moving object

3. Types of Forces:

3.1. - Gravitational force

3.1.1. - The weight of an object depends on the force of gravity pulling on that object, thus weight is the of gravitational force acting on an object. - The greater the force of gravity pulling the object, the heavier the object will be, thus unlike your mass, your weight can change. Example, a person weighing 60kg on Earth, making her 600N, but on the Moon, her weight will only be 100N. This is becausethe gravitational pull of the Moon is about one six of Earth's, hence the person's weight differs.

3.1.2. - Gravity is the pulling force exerted on all objects on earth at all times and it can act from a distance. (e.g. Earth and a ball on the ground and Earth and a box on the table.)

3.2. - Frictional force

3.2.1. - Occurs whenever two moving surfaces are in contact.

3.2.2. - Produces heat e.g. When we rub our hands together, our hands feel hot.

3.2.3. - Can be useful as without friction, we would not be able to walk or run on the ground. (e.g. Friction between the wheel and the brakes slow down the bicycle)

3.2.4. - But friction also has disavantages as it causes wear and tear and opposes motion. (e.g. Friction slows down a cyclist due to air resistance and friction causes the tires of a car and the soles of our shoes to wear out.)

3.2.5. - There are ways to overcome friction: - Having a stream-lined body shape. (e.g. Aeroplanes and fishes) - Adding rollers New node - Lubrication - Adding ball bearings

3.3. - Magnetic force

3.3.1. - Is a force exerted by magnets. Examples of magnetic materials are : Iron, Nickel, Steel and Cobalt.

3.3.2. - Magnets are used in objects like compasses or in catches for the door of a cabinet in order to keep the door of the cabinet shut and in Maglev trains. The word "magev" comes from the words "magnetic levitation" (rising and floating). The magnets in the track and the train repel each other, lifting the train a few centimeters of the track. Since there is no contact between the track and the vehicle, friction is thus reduced and hence allows the train to travel very fast, up to 500km/h.

3.3.3. - A magnet is made out of north and South poles. Like poles repel while unlike poles attract.

3.3.4. - Can be applied from a distance.

4. Can be measured with

4.1. Force-meters

4.1.1. Extension spring balance - Used by applying a force to pull the spring.

4.1.2. Compression spring balance - Used when applying a force to compress it.

5. What is Pressure?

5.1. - Pressure is the fore exerted per unit area.

5.2. - It is defined as the ratio of the force applied over the area perpendicular to the force.

5.3. We can be able push a pin into the wood but not our whole thumb as pressure has to do with the area as the tip of the pin occupies a small area, hence the force has to act only on a small area, thus giving high pressure compared to our thumb as it occupies a larger area, hence the fore has to be spread over a larger area, thus the pressure is lower.

6. How do we calculate pressure?

6.1. - The unit for pressure is Newton per square meters or Pascal (Pa).

6.2. Example, a glass block weighs 800N and is placed on the floor. Its length is 0.2m and its width is 0.1m, hence the amount of pressure on the ground is 800N divided by 0.02 meter square whoch is 40000 Pa.

7. What affects the amount of pressure?

7.1. - hence pressure is affect by two things: Fore and area. When the greater force is applied, the greater the amount of pressure. When there's a smaller area in contact, the more the pressure as well as vice versa.

8. How do we make use of pressure?

9. How is pressure used in our lives?

9.1. - When chop our food, we use a sharp knife instead of a blunt knife as the contact area between a sharp knife and the food is less compared to that of a blunt knife, hence the pressure exerted is more when using a sharp knife, allowing us to chop our food more effeciently.

9.2. - tractors have big tires in order to increase the amount of contact area between the ground and it to reduce the amount of pressure exerted on the soil.