S.H.M. Energy Flashcards
how long would an oscillator oscillate for in a closed system
forever
why
- because there are no other external forces acting on the oscillator
- that could result in the gain or loss of energy
why isnt this the case in reality however
- because (most) things dont happen in a perfect vacuum
- an oscillator in a normal environment will lose energy in various forms
- like sound energy and overcoming viscous drag against air resistance
in a closed system what is the movement of a pendulum like, simply
- the bob starts at the highest point it is set at
- when released, it swings all the way to the other side
- aligning with the horizontal plane (vertical height) it was at previously
- this motion repeats itself (infinitely in a closed system)
how does the kinetic and gravitational potential energy of the bob compare at its highest starting point
- the bob has no kinetic energy at that point as it is not moving yet
- but it has the maximum amount of GPE it can have for the given system
how does the kinetic and gravitational potential energy of the bob compare at its lowest point in the swing
- the bob has the maximum amount of kinetic energy it can have (as its velocity is highest at this point)
- but the GPE it has would be at its minimum (relative to the system it would be 0 but technically it wouldnt be)
how does the kinetic and gravitational potential energy of the bob compare at the end of one full swing
- as the bob is at its highest point again but on the other side
- it would have no kinetic energy again
- but the maximum GPE it could have
what is the transfer of energy that is going on during one whole swing
- in the beginning the GPE is being transferred to the bobs kinetic energy while it accelerates downwards
- when the midpoint (equilibrium) is reached the bob has maximum kinetic energy
- so this kinetic energy gets transferred into its GPE stores as it moves upwards
assuming this is a closed system, what is the net change in the energy of the system as this transfer of energy occurs
0
therefore what is this sum of kinetic energy and gravitational potential energy of the bob while it is in the motion of swinging equal to in this system
- the maximum GPE the bob has at its highest point
- or the maximum KE the bob has at its lowest point
on a diagram with a ‘total energy’ line on the top and a displacement line on the bottom, what would the line showing the change in GPE for one full swing look like
- the GPE line would make a symmetrical ‘U’ shape
- it would touch the total energy axis at the beginning and end
- with its minimum point touching the middle of the displacement axis
on a diagram with a ‘total energy’ line on the top and a displacement line on the bottom, what would the line showing the change in KE for one full swing look like
- the KE line would make a symmetrical ‘n’ shape
- the KE line would touch the displacement axis at the beginning and end,
- with its maximum point touching the middle of the total energy axis
what is a quality check of this graph to ensure it is accurate
- the graph should be symmetrical if a vertical line is drawn down the middle
- meaning the starting and ending points of both lines should be vertically aligned
for the KE line, what would the two point where its line touches the displacement axis be labelled as
- the point at the beginning of the axis would be -A
- the point at the end of the axis would be A
why are they labelled -A and A
- because this is the range of the swings amplitude
- from -A to 0 (equilibrium) and 0 to A
