Unit 6 Periodic Motion Flashcards
What is the period?
Time taken to complete one rotation in seconds.
What is frequency?
The number of revolutions per second in Hz.
What is angular speed?
The angle turned through per second in rads^-1.
If an object is in uniform circular motion, what conclusions can you draw from the object?
The object has a constant linear speed but a constantly changing velocity due to the object continuously changing direction. Therefore the object must be accelerating.
If an object is accelerating and is in uniform circular motion, what is this acceleration called and where is it directed towards?
This acceleration is called the centripetal (acts towards the centre of the circular path) acceleration and is perpendicular to the direction of the linear speed.
What is centripetal acceleration caused by?
Caused by a centripetal force of constant magnitude that also acts perpendicular to the direction of motion (towards the centre) so the centripetal acceleration and force acts in the same direction.
What is angular speed (⍵) of a body in circular motion is defined as?
The rate of change in angular displacement with respect to time is measured in rad s^-1.
How can you calculate angular speed (⍵) of a body ?
⍵ = Δθ/Δt where Δθ is the change in angular displacement.
What is centripetal acceleration defined as?
The acceleration of an object towards the centre of a circle when an object is in motion (rotating) around a circle at a constant speed.
If an object is moving in a circle, is it moving in equilibrium?
No, it is not moving in equilibrium, as it has a resultant force acting upon the object which is known as the centripetal force and is what keeps the object moving in a circle.
What is centripetal force defined as?
The resultant force towards the centre of the circle required to keep a body in uniform circular motion. It is always directed towards the centre of the body’s rotation.
For a vehicle going over a hill, what is its centripetal force?
For a vehicle going over a hill, what is its centripetal force?
What is the maximum speed at which a vehicle can stay in contact with the road?
V = sqrt(gr)
For a vehicle on a banked track, what is its centripetal force?
mv^2/r = Nsin(theta)
What is the velocity of a vehicle on a banked track?
v^2 = grtan(theta)
What is simple harmonic motion?
A specific type of oscillation.
What are the conditions for simple harmonic motion?
The acceleration is proportional to the displacement
The acceleration is in the opposite direction to the displacement
What is the maximum angle a simple pendulum can make with the vertical if it is to be in SMH?
10 degrees
Define damping
Process by which an oscillating object loses energy to its surrounding, which are caused by damping forces such as air resistance which decrease the amplitude of the oscillation over time
What is light damping?
This involves a small damping force, leading to a gradual decrease in amplitude
What is critical damping?
Causes the oscillation to stop in the shortest possible time, returning the object to its equilibrium position without overshooting it.
What is heavy damping?
Causes the objects to return to its equilibrium position without oscillating.
Define a free vibration
Oscillation that occurs with no transfer of energy to or from the surroundings
What are the only forces acting on a freely oscillating object?
Forces providing the resultant restoring force
What is a forced vibration?
Oscillation where a periodic external driving force is applied
State the natural frequency of an object
Frequency at which it would vibrate if left to vibrate freely with no damping or driving forces acting on it
Define resonance
Process by which a maximum in the amplitude of a forced oscillation is produced. Resonance, occurs when the driving frequency = natural frequency of an object
What is the displacement time graph for SMH?
Cosine graph
What is the velocity time graph for SMH?
-sine graph
What is the acceleration time graph for SMH?
-cosine graph
State the restoring force for a spring with spring constant k stretched by displacement x.
F = -kx
