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125 Cards in this Set
- Front
- Back
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What does the momentum of an object depend upon? |
1. Its mass 2. Its velocity |
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What is the equation for momentum? |
p=m*v
Where: • p is linear momentum • v is linear velocity • m is mass |
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What are the units for momentum? |
kgm/s (kilogram meters per second) |
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What are the units for mass? |
kg (kilograms) |
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What are the units for velocity? |
m/s (meters per second) |
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What are vectors? |
Quantities that have size and direction. |
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What is the principle of linear momentum? |
Total momentum of two objects before collision = total momentum after collision |
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What happens in an elastic collision? |
1. Momentum is conserved 2. Kinetic energy is conserved |
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What is the equation for kinetic energy? |
Ek=½mv²
Where: •Ek is kinetic energy • v is velocity • m is mass |
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What is kinetic energy measured in? |
J (Joules) |
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What happens if the collision is inelastic? |
1. Momentum is conserved 2. Kinetic energy is not conserved |
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What is Newton's second law of motion? |
F=ma
Where: • F is resultant force • m is mass • a is acceleration |
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What is resultant force measured in? |
N (Newtons) |
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What is acceleration measured in? |
m/s² (meters per second squared) |
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How do you write Newton's second law in terms of momentum? |
F=▲(mv)/▲t
Where: • F is resultant force • ▲(mv)/▲t is the rate of change of momentum |
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What is the unit for rate of change of momentum? |
kgm/s² (kilogram meters per second squared) |
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What is ▲(mv)? |
The change in momentum, ▲(mv)=mv-mu
Where: • m is mass • v is final velocity • u is initial velocity |
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What is change in momentum measured in? |
kgm/s (kilogram meters per second) |
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What is impulse? |
The product of force and time. |
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What is impulse equal to? |
The change in momentum of an object. |
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What is impulse measured in? |
Ns (Newton seconds) |
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What is the equation for impulse? |
F▲t=▲(mv)
Where: • F▲t is impulse • ▲(mv) is change in momentum |
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What is represented by the area under a force-time graph? |
Impulse |
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How can you reduce the force of an impact? |
By increasing the time of the impact. |
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What is equal to the arc length divided by the radius of a circle? |
The angle in radians |
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How many radians are there in 360°? |
2π radians |
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How do you convert degrees into radians? |
Multiply the angle by 2π/360 |
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What is angular speed? |
The angle an object moves through per second. |
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What is angular speed measured in? |
rads/s (radians per second) |
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What is the equation for angular speed? |
ω=θ/t
Where: • ω is angular speed • θ is the angle the object turns through • t is time |
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What is θ measured in? |
radians |
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What is time measured in? |
s (seconds) |
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Which equation links the linear speed and angular speed of a rotating object? |
ω=v/r
Where: • ω is angular speed • v is linear speed • r is the radius of circle of rotation |
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What is the radius measured in? |
m (meters) |
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What is frequency? |
The number of complete revolutions per second. |
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What is frequency measured in? |
rev/s (revolutions per second) or Hz (Hertz) |
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What is time period? |
The time taken for one complete revolution. |
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What is the time period measured in? |
s (seconds) |
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What equation links frequency and time period? |
f=1/T
Where: • f is frequency • T is time period |
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Which equations link angular speed and a time period of 2π? |
1. ω=2π/T
2. ω=2πf |
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What is centripetal acceleration? |
When an objects speed remains the same but it's direction is changing, meaning it's velocity is changing. |
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Which direction does centripetal acceleration always act in? |
Towards the centre of the circle |
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What is the formula for centripetal acceleration in terms of linear speed? |
a = v²/r
Where: • a is centripetal acceleration • v is linear speed • r is radius |
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What is centripetal acceleration measured in? |
m/s² (meters per second squared) |
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What is the formula for centripetal acceleration in terms of angular speed? |
a=ω²r
Where: • a is centripetal acceleration • ω is the angular speed • r is radius |
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What is Newton's first law of motion? |
An object's velocity will stay the same unless a force acts upon it. |
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What is centripetal force? |
The force causing centripetal acceleration.
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Which direction does centripetal force act in? |
Towards the centre of the circle. |
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Which two equations can be used for centripetal force? |
1. F=mv²/r 2. F=mω²r
Where: • F is centripetal force • m is mass • r is radius • v is linear velocity • ω is angular velocity |
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What happens if you remove the centripetal force from an object? |
It would fly off at a tangent with velocity v. |
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What does an object moving with simple harmonic motion do? |
Oscillate either side of an equilibrium position. |
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What is the equilibrium position? |
The midpoint of an objects motion. |
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What is displacement? |
The distance of the object from it's equilibrium position. |
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What pulls or pushes the object back toward equilibrium? |
The restoring force |
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What does the size of the restoring force depend on? |
The displacement of the object |
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What does the restoring force do? |
Makes the object accelerate towards equilibrium. |
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What can simple harmonic motion be defined as? |
An oscillation in which the acceleration of an object is directly proportional to its displacement from its equilibrium position, and is directed towards equilibrium. |
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What does a displacement-time graph for SHM look like? |
• Cosine or Sine • Maximum value A (the amplitude) |
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What does a velocity-time graph for SHM look like? |
• Gradient of displacement-time graph • Maximum value (2πf)A
Where: • f is the frequency of the oscillation |
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What does an acceleration-time graph for SHM look like? |
• Gradient of velocity-time graph • Maximum value of (2πf)²A |
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When is velocity zero on a velocity-time graph? |
When the gradient of the displacement-time graph is zero. |
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When is the acceleration at its maximum point? |
When the gradient of the velocity-time graph is maximum. |
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What is phase difference? |
A measure of the displacement between two waves. |
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What is the phase difference of two in-phase waves? |
Zero / 2π radians |
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What does two waves being in-phase signify? |
That their maxima and minima will occur simultaneously. |
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What is the phase difference of two out of phase waves? |
π radians / 180° |
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What does two waves being out of phase signify? |
One waves maxima occurs at the same time as the other waves minima. |
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How out of phase is velocity with displacement? |
• π/2 radians out of phase • Velocity is a quarter cycle ahead of displacement |
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How out of phase is acceleration with displacement? |
• 180° out of phase • In antiphase |
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What is a cycle of oscillation? |
From maximum positive displacement to maximum negative displacement and back again. |
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What is the frequency of an object moving with SHM? |
The number of cycles per second. |
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What is the time period of an object moving with SHM? |
The time taken for a complete cycle. |
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What is the amplitude of an oscillation? |
The maximum value of its displacement. |
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What is independent of the amplitude of an object moving with SHM? |
• Frequency • Time period |
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What kind of potential energy do pendulums have? |
Gravitational potential |
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What kind of potential energy do masses on springs have? |
Elastic potential |
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What does the type of potential energy depend upon? |
What's providing the restoring force. |
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What energy changes take place when an object moves towards equilibrium? |
Ep to Ek (potential to kinetic) |
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What energy changes take place when an object moves away from equilibrium? |
Ek to Ep (kinetic to potential) |
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What is an objects potential energy at equilibrium? |
Zero |
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What is an objects kinetic energy at equilibrium? |
Maximum |
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What does having a maximum kinetic energy imply? |
That velocity is maximum |
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What is an objects kinetic energy at maximum displacement? |
Zero |
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What does having zero kinetic energy imply? |
The objects velocity is zero |
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What is an objects potential energy at maximum displacement? |
Maximum |
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What is mechanical energy? |
The sum of potential and kinetic energy. |
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How does mechanical energy change? (Providing the motion isn't damped). |
It doesn't |
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What is the energy transfer for one complete cycle of oscillation? |
Ep to Ek to Ep to Ek to Ep |
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What is the equation for the displacement of an object moving with simple harmonic motion? |
x=Acos(2πft)
Where: • x is displacement • A is amplitude • f is frequency • t is time |
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What is displacement measured in? |
m (meters) |
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What is amplitude measured in? |
m (meters) |
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What is the equation for the acceleration of an object moving with simple harmonic motion? |
a=-(2πf)²x
Where: • a is acceleration • f is frequency • x is displacement
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When does maximum acceleration occur? |
When the object is at maximum displacement. |
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What is the equation for the maximum acceleration of an object moving with simple harmonic motion? |
a-max=(2πf)²A
Where: • a-max is the magnitude of maximum acceleration • f is frequency • A is amplitude |
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What is the equation for the velocity of an object moving with simple harmonic motion? |
V=±2πf√(A²-x²)
Where: · v is velocity · f is frequency · A is amplitude · x is displacement |
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When is an objects velocity greatest?
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When it is moving through equilibrium.
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What is the equation for the maximum velocity of an object moving with simple harmonic motion?
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v-max=2πfA
Where: · v-max is max velocity · f is frequency · A is amplitude |
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What are two examples of simple harmonic oscillators?
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· A mass-spring system
· Pendulums |
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What does Hooke's Law tell you?
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The size and direction of the restoring force for a mass-spring system.
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What is Hooke's Law?
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F=-kx
Where: · F is the restoring force · k is the spring constant · x is the displacement |
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What does Newton's second law state?
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The resultant force on an object is equal to the mass of the object times its acceleration.
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What is the equation for time period of a mass-spring system?
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T=2π√(m/k)
Where: · T is the period of oscillation · m is mass · k is the spring constant |
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What is the time period squared of a mass-spring system proportional to?
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· Mass
· The inverse of the spring constant |
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What happens to the time period of a mass spring system if you change the amplitude?
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Nothing
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What is the formula for time period of a simple pendulum?
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T=2π√(l/g)
Where: · T is the period of oscillation · l is the length of the pendulum · g is the gravitational field strength |
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What is the time period squared of a simple pendulum proportional to?
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· Length of the pendulum
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What is the time period of a simple pendulum independent from?
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· The mass of the bob
· The amplitude of the oscillation |
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If an oscillator is vibrating freely what does that mean?
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The object is oscillating at its natural frequency, there is no energy transfer to or from the objects surroundings.
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When do forced vibrations occur?
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When there's an external driving force.
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What is the driving frequency?
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The frequency of the external force
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When does resonance occur?
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When the natural frequency matches the driving frequency.
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What happens during resonance?
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The amplitude of oscillation rapidly increases.
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What is the phase difference between the driver and the oscillator when resonance occurs?
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90˚
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What is damping?
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When an oscillating system loses energy to it's surroundings.
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What can naturally cause damping?
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Frictional forces such as air resistance.
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Why would you want to use damping?
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To minimise the effect of resonance.
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What does damping do?
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Reduces the amplitude of oscillation over time.
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What are the effects of light damping?
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· Oscillations are take a long time to stop
· The amplitude of each oscillation is only reduced by a small amount each period |
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What are the effects of heavy damping?
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· It only takes a small amount of time to stop oscillating
· Amplitude is greatly reduced with each period. |
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What is critical damping?
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Critical damping reduces the amplitude in the shortest possible time.
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What is overdamping?
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Very heavily damped systems.
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What is the effect of overdamping?
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The system takes longer to return to an equilibrium position then a critically damped system.
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What can overdamping be used for?
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Making sure heavy doors don't close too quickly.
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Other then damping, what also reduces the amplitude of oscillations?
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Plastic deformation of ductile materials.
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Why does plastic deformation cause a reduction in amplitude?
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The material absorbs energy as it changes shape.
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