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76 Cards in this Set
- Front
- Back
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What is the definition and equation for momentum? |
Momentum = mass* velocity or p = mv |
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State Newtons three laws of motion. |
1) A body continues in it’s state of rest or linear motion unless acted upon by an external force 2) When a force acts on a body, the force is proportional to it’s rate of change of linear momentum (F = ma). 3) To every action there is an equal and opposite reaction. |
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What is the full equation for impulse? |
Force*time = change in momentum |
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If you had a graph of force against time, how would you find the change in momentum? |
Take the area under the graph. |
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What is the principle of conservation of momentum? |
During any collision or explosion, the total momentum before equals the total momentum afterwards. |
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What does it mean if a collision is elastic? |
Kinetic Energy is conserved. |
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What does it mean if a collision is partially inelastic? |
That the colliding objects move apart, and have less kinetic energy after the collision than before. |
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What happens during a totally inelastic collision? |
The objects stick together and kinetic energy is lost. |
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In an explosion question, normally what would the initial momentum be? |
zero |
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What is the equation for the linear velocity of an object moving in a circle of radius r and period T? |
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Draw a diagram that shows one radian. |
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What is the equation for angular velocity, "w" , based on it’s definition? |
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What is the equation for angular velocity if you were given the period T? |
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What equation links period and frequency? |
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What equation links linear and angular velocities? |
V= rw |
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What is the equation for acceleration for an object moving in a circle of radius r with linear velocity v? |
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What is the equation for centripetal force if you are given linear velocity v? |
f |
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What is the equation for centripetal force if you are given linear velocity v? |
f |
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What is the equation for centripetal force if you are given angular velocity ? |
f |
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Draw the forces on a person in a car going over the top of a hill. |
v |
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What is the definition of Simple Harmonic Motion? |
v |
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What condition is true if something is performing Simple Harmonic Motion? |
v |
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What is the equation for the phase of an oscillation? |
v |
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In Simple Harmonic Motion, what equation links acceleration with displacement? |
v |
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Sketch graphs of displacement, velocity and acceleration for an object performing Simple Harmonic Motion showing their phase relationship. |
v |
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What is the equation for the period of a pendulum? |
v |
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What is the equation for the period of a mass on a spring? |
v |
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Sketch a graph showing how Potential and Kinetic energy vary during Simple Harmonic Motion. |
v |
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What is damping? |
When an oscillator loses energy during each cycle so it’s amplitude gradually decreases. |
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What is resonance? Give three examples. |
An oscillator being driven at it’s natural frequency. The amplitude rises to a high value.
Microwave ovens, marching over bridges, Barton’s pendulums etc. |
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What is the definition of a field? |
A region where something experiences a force due to one of it’s properties. |
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What is Newtons equation for the force between two masses separated by distance r? |
v |
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What is the definition of field strength? |
The amount of force experience by a unit of the affected property. |
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What is the equation for gravitational field strength, based on Newton’s equation? |
v |
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From a diagram of a field, how would you know it was uniform? |
The lines are parallel, straight and equally spaced. |
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What is the equation for gravitational Potential? |
vv |
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What is the definition of potential? |
The energy that a unit of the affected property has at that point in the field. |
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Sketch a graph showing how the field strength of the Earth varies as you go from it’s center out into space. |
v |
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What needs to be true in order for a satellite to stay in orbit? |
All the gravitational force of attraction supplies exactly the right amount of centripetal force for that radius and velocity, 0r IMAGE........ |
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What is a black hole? |
An object who’s gravitational field is so high, the escape velocity is greater than the speed of light. |
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What is the equation for Kinetic Energy? |
v |
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What are the rules for drawing electric field lines? |
They: start and end on a charge go from positive to negative, leave surfaces perpendicular, find the shortest route and do not cross. |
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What is the definition of electric field strength? |
The force acting on 1 coulomb at that point in the field. |
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What is the equation for electric field strength based on the definition? |
v |
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What is the equation for the field strength between two parallel plates separated by a distance d and with voltage v across them? |
v |
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What is the equation for electrical current based on it’s definition? |
v |
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What is the equation for electrical current based on it’s definition? |
The energy that one coulomb has because of where it is in the field. |
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What is Coulomb’s equation for the force between two charges separated by distance r? |
v |
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What is the equation for electric field strength based on Coulomb’s equation? |
v |
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What is the equation for electric potential based on Coulomb’s equation? |
v |
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What equation links charge and voltage for a capacitor? |
Q = CV |
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What are the two common forms of the equation for the energy stored on a capacitor? |
v |
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What equation would you use to find how much charge was left on a capacitor if it had initially been charged to Q0 coulombs but has been discharging for t seconds through a resistor R? |
v |
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Sketch a graph showing how charge varies with time for a discharging capacitor? Use this diagram to show what the time constant is. |
g |
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Draw a diagram which shows the motor effect. |
g |
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What is the force on a wire of length l carrying current I in a magnetic field? |
F = BIL |
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What is the force on an electron travelling at velocity v perpendicular to a magnetic field? |
F = Bev |
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What is a couple? |
Two equal and opposite forces separated by a distance perpendicular to the forces. Their effect is to turn an object rather than move it up/down left/right etc... |
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What is the equation for the maximum torque on a coil of area A carrying a current I in a magnetic field if the coil has n turns? |
torque = BIAn |
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What is the Hall Effect? What is the equation for the Hall Voltage? |
The separation of charge based on it’s charge (positive or negative) as it moves through a conductor in a magnetic field. The effect is that at voltage (the Hall Voltage) is generated across the top and bottom of the conductor (assuming the field and current are horizontal and perpendicular). Hall Voltage VH = Bvd. |
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Draw a diagram showing the parts of a cyclotron. |
g |
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What are the two forms of Faraday’s Law? |
1) When a conductor cuts a magnetic field, the emf induced is proportional to the rate at which the flux is cut. 2) When the flux linked with a circuit changes, the emf induced is proportional to the rage of change of flux linkage. |
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What is flux linkage? Give the equation. |
This is the flux multiplied by the number of turns of a coil that are experiencing it in order to get the total effect. EQUATION.... |
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What is Faraday’s Law as an equation? |
g |
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What is Lenz’s Law? |
The direction of an induced current is such that it opposes the change causing it. |
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Draw a solenoid showing the shape and direction of the current through it and the magnetic field around it. |
g |
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What is meant by “back emf”? |
The emf induced in a motor due to the generator effect. It opposes the driving voltage so has the effect of lowering it. |
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What is the equation for the emf induced in a moving conductor of length l in a magnetic field? |
g |
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What is the equation showing how the induced Emf varies or alternates over time in an AC generator? |
g |
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What is the equation for electrical power? |
g |
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What equation links the voltage applied, back emf, current and load resistance for a motor? |
g |
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Why is the current in a motor much less than you would expect if it is turning fast? |
The back emf opposes the driving voltage and lowers it’s value. The resistance of the coil is still the same so the current also decreases. |
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What is a transformer? |
Two coils of wire, the primary and secondary coils. One produces a changing magnetic field (from an AC current). The other sits in that field and has an induced emf due to it. The number of turns determines the voltage so they are used to change voltages. |
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What equation describes how voltage, current and number of turns are linked for a transformer? |
g |
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Why is electricity distributed at high voltage? |
If the voltage is high, the current is low, so this minimises loss due to heating. |
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What is efficiency? |
The ratio of energy delivered to energy sent, often expressed as a percentage. It represents how much of the energy sent actually gets to it’s destination, i.e. is not lost. |
