Unit 4 Flashcards
What is the principle of linear momentum?
Total momentum of two objects before they collide is equal to the total momentum after they collide assuming no external forces act.
Define elastic collision
A collision where kinetic energy is conserved
Inelastic collision
Collision where kinetic energy isn’t conserved
In a Inelastic collision what other forms could the energy be converted into?
Heat energy, sound energy, or energy into damaging the vehicles
What is newtons 2nd law
Force is proportional to the rate of change of momentum
What is impulse
Impulse is force x time and equal to the change in momentum
What is represented by the area under a force time graph?
Impulse or change in momentum
Why are objects moving in a circle constantly accelerating even though they are travelling at constant speed?
The centripetal force acts perpendicular to the objects velocity causing it to move in a circle and velocity is constantly changing even though speed I constant because the direction it is moving in is always changing
Where is the acceleration towards when an object is moving in a circle?
Toward the centre of the circle
Define simple harmonic motion
Oscillations in which the acceleration is directly proportional to the displacement and acting in the opposite direction (towards equilibrium)
Defining equation of SHM
A=(2pif)^2 x
What is the phase difference between the velocity and displacement of an object undergoing SHM.
Pi over 2 (1/4 of a wave cycle)
What is the phase difference between the acceleration and displacement of an object undergoing SHM?
Pi radians - they are completely out of phase
What is the relationship between the amplitude and time period of a simple pendulum?
They are independent of each other - the time period is the same no matter what the amplitude of oscillation is
What are the two types of potential energy in a spring- mass system
Gravitational and elastic potential
When is the kinetic energy + potential energy = constant?
In an undamped system
How can you derive the equation of the time period of a mass spring system?
Using f=ma where F=kx (hookes law) and simple harmonic equTion for acceleration
How do you work out the spring constants of springs in parallel? (Side by side)
K(total)=k1 +k2 +…
How do you work out the springs constant of springs in series?
The inverse of the spring constants are added together
What is a free oscillation
Oscillation with no transfer of energy to and from the surroundings- there is no driving force acting and the object oscillates at its natural frequency
What causes forced vibrations?
A periodic external force
When does resonance occur?
When the driving frequency equals the natural frequency
At driving frequencies lower than the natural frequency what is the phase difference?
No phase difference they are in phase
What is the phase difference between the driver and oscillator at resonance?
Phase difference between the oscillator and driver is 90 degrees (Pi over 2)
Phase difference between driver and oscillator at frequencies higher than the natural frequency
Driver completely out of phase
What does damping do to SHM oscillations
Decrease the amplitude
Define light damping
The amplitude of oscillation reduces a small amount with each period and can take a long time to stop oscillating
Define heavy damping
Amplitude gets much smaller in a short space of time and stop oscillating quicker than a lightly damped system
Define Critical damping
Reduces amplitude and stops the system oscillating in the shortest time possible
Where can critical damping be used?
In car suspension systems
Deign overdamping
Take longer to reach equilibrium than critically damped systems
Example where overdamping is used and explain why
Heavy doors- they are over damped so they don’t slam shut too quickly, they close slowly to give People time to walk through them
Explain the difference in resonance graphs for damped systems and what happens to when resonance occurs for heavily damped systems
Lightly damped systems have a very sharp resonance peak where as heavily damped systems have a latter response. For heavy damping resonance occurs at a slightly lower driving frequency than the natural frequency.
Examples of uses of damping
Bridges/buildings - damped to avoid them being damaged by resonance in regions prone to earthquakes. Heavy masses move in opposite direction to building to dampen the oscillations - critical damping. Other uses are loud speakers
Define gravitational,field strength
Force per unit mass
Define gravitational potential
Work done per unit mass in moving the object from infinity to that point in the gravitational field
What is the gradient of a gravitational potential against distance graph?
Field strength
What is the area under a field strength-distance graph
Gravitational potential
What is the gravitation potential at a infinite distance from the mass
0
Gravitational potential is always…
Negative
Momentum- vector or scalar
Vector
