Forces
- Created by: Aaisha_Syed
- Created on: 02-06-20 11:15
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- Forces
- Vectors and scalars
- Force is a vector quantity. Vector quantities have a magnitude and a direction
- Lots of physical quantities are vector quantities. Vector quantities include: force, velocity, displacement, acceleration, momentum, ect.
- Some physical quantities only have magnitude and no direction. These are scalar quantities.
- Scalar quantities include: speed, distance, mass, temperature, time, etc.
- Vectors are usually represented by an arrow. The length of the arrow shows the magnitude. Velocity is a vector, but speed is a scalar quantity.
- Contact and non-contact forces and resultant forces
- A force is a push or a pull on an object that is caused by it interacting with something. All forces are either contact or non-contact forces.
- When two objects have to be touching for a force to act, that force is called a contact force.
- If the objects do not need to be touching for the forces to act, that force is a non-contact force.
- When two objects interact, there is a force produced on both objects. An interaction pair is a pair of forces that are equal and opposite and act on two interacting objects.
- Work Done
- When a force moves an object through a distance, energy is transferred and work is done on the object.
- To make something move, a force must be applied. The thing applying the force needs a source of energy. The force does 'work' to move the object and energy is transferred from one store to another.
- Whether energy is transferred 'usefully' or is 'wasted' you an still say that 'work is done'. Work done = Force x Distance.
- When a force moves an object through a distance, energy is transferred and work is done on the object.
- Parallelogram and resolution of forces.
- In most real situations there are at least two forces acting on an object along any direction. If you have a number of forces acting on a single point, you can replace them with a force. The 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 subtracting any going in the opposite direction.
- Gravity and centre of Mass
- Gravity attracts all masses, but only notice it with when one of the masses is really big like a planet. Anything near a planet or star is attracted to it very strongly. The two important effects is on the surface of a planet, it makes all things fall towards the ground and it gives everything a weight.
- Mass it the amount of 'stuff' in an object. For any object, this will have the same value anywhere in the universe.
- Weight(N) = Mass(kg) x Gravitational Field Strength (N/kg)
- Required Practical- stretching a spring
- Equipment: Spring, Clamp, Fixed ruler, Extra masses, hanging mass, weighted stand and tape.
- Method: 1) Measure the length of the spring with a millimetre ruler clamped to the stand. Make sure you take the reading eye level an add a marker to the bottom of the spring to make the reading more accurate.
- 2) Add a mass to the spring and allow it to come to rest. Record the mass and measure the new length of the spring. The extension is the change in length. 3) Repeat the process until you have enough measurements (no fewer than 6.)
- 4) Plot a force-extension graph of your results. Elastic potential energy(J) = 1/2 x spring constant (N/m) x extension (m) squared.
- 2) Add a mass to the spring and allow it to come to rest. Record the mass and measure the new length of the spring. The extension is the change in length. 3) Repeat the process until you have enough measurements (no fewer than 6.)
- Forces and Elasticity
- Hooke's Law: Force(N) = spring constant(N/m) x Extension(m)
- Elastic potential Energy(J) = 0.5 x Spring Constant (N/m) x extension (m) squared.
- Elastic Potential Energy is the energy stored in anything that is stretched or squashed. The amount of energy depends on how much the thing is stretched or squashed. We cal this the extension. To work out the extension you do: extension = new length - old length. The extension is measured in metres. The EPE also depends on spring constant, which tells us how easy or difficult it is to stretch the thing.
- Vectors and scalars
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