Physics - Forces Revision
- Created by: CharlotteMcW
- Created on: 02-06-20 10:12
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- Forces
- Scalars and Vectors
- The difference between Scalars and Vectors is that Vectors must have a specific direction, whereas Scalars don't.
- Three examples of Scalars are distance, speed, mass.
- Three examples of Vectors is force, velocity, displacement.
- Vectors have magnitude and direction.
- Scalars have only magnitude and no direction.
- Vectors are usually represented by an arrow.
- The length of the arrow shows the magnitude and the direction of the arrow shows the direction of the quantity
- Contact and Non Contact Forces + Resultant forces
- Contact Forces - two objects have to touch each other to feel a force
- An interaction pair is a pair of forces that are equal and opposite and act on two interacting objects.
- Non Contact Forces - two objects feel a force without touching.
- If you push or pull something, you make a pair of forces.
- They are the same size but with different directions.
- A resultant force is the overall force on a point or object.
- If you have a number of forces acting on a single point, you can replace them with just one force.
- This single force is called the resultant force.
- If the forces all act along the same line, the overall effect is found by adding those going in the same direction, and subtract those going in the other direction.
- If you have a number of forces acting on a single point, you can replace them with just one force.
- Contact Forces - two objects have to touch each other to feel a force
- Work done
- When a force moves an object through a distance, energy is transferred and work is done on the object.
- Whether energy is transferred usefully or is wasted, you can still say "work is done"
- You can find out how much work has been done by using an equation.
- W=fs Work done = Force x Distance
- When a force moves an object through a distance, energy is transferred and work is done on the object.
- Gravity and Centre of Mass
- Gravitational force is the force of attraction between masses.
- Weight and mass are not the same.
- Mass is just the amount of "stuff" in an object.
- Mass is not a force. It is measured in kilometres.
- Weight is the force acting on an object due to gravity.
- Close to earth, this force is caused by the gravitational field around earth.
- Gravitational field strength varies with location.
- The weight of an object, depends on the strength of the gravitational field.
- For example, on earth and the moon a person would have the same mass but not the same weight.
- Weight is a force measured in Newtons.
- Close to earth, this force is caused by the gravitational field around earth.
- Mass is just the amount of "stuff" in an object.
- Required practical: stretching a spring.
- 4 simple steps : 1. Measure the natural length of the spring with a millimetre ruler. 2. Add a mass to the spring and allow it to come to rest. Measure the new length of the spring. 3.Repeat this process until you have enough measurements. 4. Plot a graph of your results.
- Forces and Elasticity.
- Hooke's Law: Force = Spring Constant x Extension
- Work done in stretching a spring : elastic potential = 0.5 x spring constant x (extension)squared.
- Scalars and Vectors
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