Further mechanics Flashcards
(36 cards)
Where does the centripetal force act?
Towards the centre of the circle
Why is an object travelling at a constant speed in circular motion still accelerating?
The direction at which the object is travelling is constantly changing meaning that although the speed is constant, the velocity of the object is constantly changing (as velocity is a vector), therefore if the velocity is changing then the object must be accelerating (because acceleration is a change in velocity over a time period)
What happens if the centripetal force of an object is circular motion is suddenly removed?
The object will travel in a straight line in the direction of the tangent at the point at which the force was removed
Why can’t a centripetal force cause an increase in speed?
The force always acts perpendicular to the velocity of the object meaning no work is being done (as there is no component of the force acting in the direction of movement), so if no work is being done, there is no change in kinetic energy hence no change in speed
What is angular speed?
The rate at which an object rotates through an angle (the angle it rotates through per second)
What is centripetal acceleration?
The acceleration towards the centre of the circle that keeps the object moving in circular motion
What is meant by centripetal force?
The net force required to keep an object moving in circular motion at a constant speed
What is frequency in terms of an object moving in circular motion?
It is the number of complete revolutions per second
Explain why banked corners are used by cars to take corners at high speeds
When a car travells around a flat corner, the friction between the tyres and the road must provide all of the centripetal force needed to keep the car moving in a circle, however if the corner is banked, the road is tilted so instead of the normal reaction force acting vertically upwards it acts at an angle, meaning it has a component acting towards the centre of the circle helping to contribute to the centripetal force, meaning less friction is needed and the car can travel faster without skidding
What does simple harmonic motion look like?
In simple harmonic motion, the object oscillates back and forth about an equilibrium position, the motion is symmetrical, with constant frequency and maximum displacement at the amplitude
What is the condition for an object to be undergoing simple harmonic motion?
The acceleration of the object must be directly proportional to the negative of its displacement from its equillibrium position
Draw the graph of a against x for SHM
Look in booklet for answer
What is a restoring force?
The force that brings the thing that is oscillating back to the equilibrium position
Draw the SHM graphs for displacement, velocity and acceleration
Look in booklet for answers
Describe how the displacement, velocity and acceleration vary during one oscillation of a pendulum
At the miniumum amplitude the displacement is at a minimum, the velocity is zero and acceleration is at a maximum, then as the pendulum moves from the minimum amplitude to the equilibrium position the displacement increases up to 0, the velocity increases up to a maximum and the acceleration decreases down to 0, then as the pendulum moves from the equilibrium position up to a maximum amplitude the displacement increases up to a maximum, the velocity decreases down to a minimum and the acceleration decreases down to a minimum
(then this whole process repeats for the other half of the oscillation)
Draw the graph showing the variation of kinetic, grativational potential and total energy with displacement
Look in booklet for answer
Describe the energy transformations that occur in a simple pendulum
As the pendulum moves from the amplitude to the equilibrium position GPE is transferred into KE and as it moves from the equilibrium position to the amplitude KE is transferred to GPE
What is a free vibration?
An oscillation that occurs when an object or system is displaced from its equilibrium position and then allowed to oscillate without any external forces (no driving force) acting on it apart from the object or systems restoring force
What is natural frequency?
The frequency of an object that is in free vibration (has no driving force it is just oscillating freely)
What is a forced vibration?
An oscillation that occurs when an object or system is continuously driven by an external force at a certain frequency (hence it has a driving force)
What is resonance?
When the driving frequency of an external force is equal to the natural frequency of a system, resulting in a large increase in the amplitude of the system
Give some examples of resonance
- A radio is tuned in so the electric circuit resonates at the same frequency as the radio station you want to listen to
- A glass resonates when driven by a sound wave at the right frequency
- A swing resonates if it is driven by someone pushing it at its natural frequency
What is damping and what can cause it?
Damping is the process by which energy is gradually lost from an oscillating system, which reduces the amplitude of the oscillations, this can be caused by air resistance, friction, internal material resistance etc…
What is critical damping?
A resistive force that returns an oscillating system to equilibrium in the shortest possible time without overshooting or oscillating
