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# Physics - Miss Casey

### Physics - Unit 1 - OCR

What is the net force equation? Net force = mass X accceleration
What is a force? Anything that causes acceleration.
What relates force to acceleration? Mass -the large the mass, the harder it is to accelerate.
What is the resultant force of an object? The total or overall force.
The net force is the vector sum of all the ...... acting on an object. i.e. all the .......... are taken into account. The net force is the vector sum of all the forces acting on an object. i.e. all the directions are taken into account.
What did Einstein say about Newton's Second Law? As objects travel nearer to the speed of light, their mass increases.
What is the acceleration due to free fall on Earth? 9.81 ms-2
What is the equation to work out the weight of an object? Weight = mass X acceleration of free fall
Define mass: Mass is a measure of the amount of a substance in an object. It's units are in kg and does not vary with position.
Define weight: Weight is a force caused by an objects position in a gravitational field. It has units of newtons.
What are the 5 types of force? (hint: GEFET) Gravity, Electrical, Friction, Elastic and Tensile.
If the acceleration due to free fall is the same for all objects, then what effects an objects speed? Drag affects an objects speed.
What five things affect the amount of drag on an object? The speed of the body, the size of the body, shape of the body, roughness of the body, fluid through which it is moving.
An object falling from a height experiences two forces, drag and weight. What is reached when these two forces are balanced? Terminal velocity.
What are the nine forms of energy? Kinetic, heat gravitational, electric, light, sound, nuclear, elastic and chemical.
What does the law of conservation of energy state? Energy cannot be created or destroyed only converted from one form to another.
What is the work done equation? force X distance moved in the direction of the force
work done = what? Energy transferred.
What is the kinetic energy equation? 1/2mv(squared)
What is the equation to work out GPE? GPE = mass X acceleration due to free fall X height
What is power? The rate which work is done.
What is the equation to work out power? power = work done/ time taken
What are the units of power? Watts
What is the equation for working out efficiency? efficiency = useful energy output/total input X100%
What are Sankey diagrams and what do they show? They are a type of flow diagram, they show the amount of energy involved and where it all goes, eventually showing how much is actually useful energy. The width of the arrows are proportional to how much energy is involved.
How do you work out stopping distance? stopping distance= thinking distance + braking distance
What is the thinking distance of a car? The time from when the driver sees the obstacle to when the driver presses the brakes.
What is the braking distance of a car? During braking the brakes are doing work on the car, they have to convert energy from one form to another. So the faster the car is going, the longer it is going to take the brakes to bring the car to a complete stop.
Is power a scalar or a vector? Scalar.
What is 1 watt? One joule of energy transferred per second.
What are some features that increase car safety? Crumple zones, airbags, automatic stopping, reversing sensor and seat belts.
Acceleration is the rate of change of velocity, what is the equation for this? (v-u)/t. Where V is the final velocity, U is the initial and T is the time taken.
What are crumple zones? They are areas of a vehicle that are designed to deform and crumple in a collision, this absorbs some of the energy of the impact, preventing it being transmitted to the occupants. They bring the car to a stop slower than if it was rigid.
The longer the time it takes for the car to decelerate, the less ..... on the car. The longer the time it takes for the car to decelerate, the less force on the car.
What is the job of the seatbelt? Stop the driver hitting the sterring wheel/windscreen. Spread the stopping force across sturdier areas of the body. Stretches a little to slow them down slower.
What happens to an airbag when a car crashes? An accelerometer measures acceleration it experiences relative to free fall, when you stop rapidly the accelerometer sends a signal which tells the bag to inflate. It is inflated from a chemical reaction that produces nitrogen gas, at over 200mph.
Once an airbag is inflated, what happens? The air dissipates through tiny holes in the bag thus deflating the bag so you can move.
What does the airbag register as a car crash? The US regulation require deployment in crashes at least equivalent in deceleration to a 14mph collision. Side on collisions have different decelerations and so sometimes may not result in deployment.
What is Trilateration? Data from three satellites narrows the position down to the area where the three spheres overlap. This provides a relatively accurate position.
What is an atomic clock? The most accurate timing device ever made. The clock's rate is controlled by the frequency of an internal motion within an atom. Time is now define by a particular motion of an electron and nucleus within the caesium atom.
Define Deformation: A change in the shape or size of an object due to the action of a force.
What is an elastic body? An elastic body is one that returns to it's original shape after the force is removed.
What is a plastic body? A plastic body is one that does not return to it's original shape after the force is removed.
What is the difference between an elastic collision and an inelastic collision? An elastic collision loses no energy. The deformation on collision is fully restored, whereas in an inelastic collision energy is lost and the deformation may be permanent.
What does Hooke's law state? That extension is proportional to force. It applies to springs, but he discovered it using a metal wire.
When does Hooke's law stop working? When the load is great enough.
The spring constant is a measure of what? The stiffness of material. If the spring is very stretchy the 'K' is low, whereas if it is stiff the 'K' is high.
What does Hooke’s law state? The force applied is proportional to extension of a spring up to the elastic limit.
The work done in a spring is equal to what? The strain energy stored in the spring. Which means it equals: force X distance moved in the direction of the force.
What happens if a material is stretched beyond it’s elastic limit? It begins to behave plasticly. Permanent deformation occurs, and the material does not return to it’s original shape once the force is removed.
What is Hysteresis? Energy lost in stretching a rubber band.
When stretching a wire, the extension depends on what four factors? - It’s original length. - The load stretching it. - The cross sectional area of the wire. - The stiffness of the material of which it is made the spring constant k.
What is a tensile stress? When equal and opposite forces are directed away from each other.
What is a compressive stress? When equal and opposite forces are directed towards each other.
What is the equation to work out stress? Stress = F/A
Define stress: The force applied to a material per unit area (n/m^^2) (^^ means to the power of)
What is the equation to work out strain? Strain = change in length/ original length
Define strain: The change in length divided by the original length (unless they cancel out)
What is the ultimate tensile strength? (UTS): The ultimate tensile strength is the greatest stress a body can experience without breaking or rupturing.
What is the equation to work out the youngs modulus of a material? young’s modulus = stress/strain
What is the young’s modulus of a material? It is a measure of the stiffness of a material.
What is a ductile material, and what type of graph do they produce? A ductile material can be stretch a long way past it’s elastic limit before breaking. It produces a straight line graph with a curve at the top.
What is a brittle material, and what type of graph do they produce? A brittle material snaps when it reaches it elastic limit. It produces a straight line graph.
What is a polymeric material, and what type of graph do they produce? A polymeric material does not show linear behaviour (e.g. rubber.) It produces a small curve at first then flattens out, then curves upwards at the end.
Created by: Sparksy

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