Wave behaviour Flashcards
What is simple harmonic motion
Acceleration is directly proportional to displacement in a negative direction, from a fixed point and has always directed to that fixed point
What is an oscillation
Repetitive variation of the displacement of an object about the equilibrium
How do you make a pendulum swing quicker
A pendulum is only dependent on length therefore if you shorten the length the pendulum will swing quicker
For a pendulum what would the graph for displacement against time look like
The graph would start at a positive displacement and would curve down to create a minimum in the negative values before curving up to create a maximum before coming down again, and so on. It will look a little bit like a cos graph
On a displacement graph for a pendulum what does the roots of the graph mean, and what does the max and min areas of the graph mean
The roots of the graph mean the equilibrium points where displacement equals zero, the maximum and minimum points show the highest displacement of the pendulum
What is the amplitude
Displacement on either side of the graph. Measured in metres
What is wavelength
The distance between two successive points on a graph for example from peak to Peak or trough to trough
What is a period
The time interval for one complete oscillation measured in seconds
What is it called if the oscillations have a constant period
This is called isochronos. This means all cycles are at the same period
What is frequency
The number of oscillations per second measured in Hertz or Hz
What is angular frequency
The rate of change of angular displacement with respect to time (rads^-1)
How do you convert milliseconds into seconds
divide the milliseconds by 1000
How do you convert from radians to degrees and vice versa. What is a good way to remember this?
To convert radians to degrees:
Radians = pi/180 x degrees
Degrees = 180/pi x radians
- To convert radians to degrees, pi should be on the numerator
- to convert from degrees to radians, 180° should be on the numerator
What is the force responsible for the motion in simple harmonic motion
Restoring force. This force is always directed towards the equilibrium point
What is acceleration directly proportional to in simple harmonic motion
Acceleration is directly proportional to displacement in the negative direction
The acceleration against displacement graph look like for simple harmonic motion
There should be a straight diagonal line with a negative gradient going through the origin. It should start at the top of the second quadrant and end at the bottom of the fourth quadrant
Why is a person jumping on a trampoline not an example of simple harmonic motion
- the restoring force is equal to their weights which is constant
– on a trampoline, the jumper can always jump higher and change displacement which is not allowed for simple harmonic motion
– the restoring force on the person is not proportional to the distance from the equilibrium position
What are the conditions for simple harmonic motion
- the restoring force is proportional to the displacement (this means that X force, should only take me to a Y displacement)
– the restoring force is opposite to the direction of the displacement
What do the displacement, velocity, and acceleration graphs look like against time for a pendulum? And how can you remember that?
For displacement:
The graph would look like a cos graph, where the roots are where the pendulum is at the equilibrium point and the maximum and minimum is when the pendulum is at its maximum displacement
for Velocity:
The velocity graph will look like a sign graph that has been reflected in the x axis. On this graph minimum and maximum points will be when the pendulum is at its equilibrium .
For acceleration:
The graph will look like a cos graph reflected in the x axis. At the roots of the graph is the equilibrium point of the pendulum
How to remember them:
For displacement, you start at the top
For velocity, you start at the middle
For acceleration, you start at the bottom
When is the displacement highest on a pendulum?
When it has been pulled up to its maximum height
When is the velocity highest on a pendulum? why
At the equilibrium point. As the pendulum swings down from its maximum displacement (the highest point), gravitational potential energy is converted into kinetic energy.
At the equilibrium position, all the available potential energy has been converted into kinetic energy, meaning the pendulum reaches its maximum speed.
After passing through the equilibrium position, the pendulum starts to swing upward, and the kinetic energy begins converting back into potential energy, causing the velocity to decrease.
When is acceleration highest on a pendulum? and why?
At the end points, the pendulum momentarily stops before reversing direction, meaning its velocity is zero.
However, the force pulling the pendulum back toward the center (due to gravity) is greatest at these points, creating the maximum acceleration.
This acceleration is directed toward the center (the equilibrium position), and it is entirely due to the restoring force acting along the path of the swing.
