Periodic Motion and Waves Flashcards
Is the relationship between wavelength and frequency linear?
No, because v = wavelength * frequency and when you plot a graph of wavelength and frequency, you got frequency = v/wavelength so it looks more like y = 1/x graph
If an object has changing speed, is kinetic energy conserved?
Nope
If there is an external force acting on a pendulum, is momentum conserved?
Nope, external forces like gravity and tension do not conserve momentum
If an object does not have conserved kinetic energy, can it still have conserved momentum?
No because if kinetic energy is not conserved like if speed keeps changing then that means momentum is changing too because p = mv
How do you find tension when a pendulum is swinging through the lowest point?
F(tension) - F(gravity) = F(centripetal)
T - mg = (mv^2)/r
This is because the pendulum is swinging in the arc of a circle
In a standing wave, where is the antinode?
It’s where the amplitudes are
In a simple harmonic oscillation, where is kinetic energy and potential energy at there maximum?
Kinetic energy at maximum when it is at equilibrium.
Potential energy at maximum when it is at maximum amplitude.
Are frequency and period dependent or independent of amplitude in SHO?
Independent
As a mass moves from initial amplitude to equilibrium, what happens to the speed and acceleration?
Speed increases and acceleration decreases
What is the equation for period of spring system?
T = 2pi* sqrt(m/k)
What is the equation for period of pendulum system?
T = 2pi* sqrt(L/g)
What are the units for spring constant (K)?
N/m or kg/s^2
A pendulum swings one complete cycle and returns to maximum height, when the cable is cut, what happens to the velocity of the pendulum object?
v = 0 at this point because it is at maximum height and because the only force acting on it is gravity now (no more tension), the object will fall straight down
Where in a cycle of a pendulum is the kinetic energy equal to the potential energy?
Halfway between the KE max and PE max. So at t = pi/4, 3pi/4, 5pi/4, 7pi/4
How are standing waves formed?
Waves of equal amplitude traveling in opposite directions
Changing the mass on a horizontal spring will have what affect on KE and PE? What about speed? Assume same initial displacement.
KE and PE will still stay the same because since the initial displacement stayed the same PE must be the same. However, the speed will decrease because the mass increased and KE = 0.5mv^2
If a mass is attached at both ends of two springs, what is the PE at any point?
Because there are two springs, you add up PE from each individual spring so you get kx^2
How does a heavier mass affect period of an oscillator?
It will increase period because heavier masses oscillate more slowly
How does a stiffer spring, greater k, affect the period of an oscillator?
A stiffer spring will pull the mass back to equilibrium faster, so the period will be decreased
With two springs, the effective spring constant is?
Doubled because you add up both spring constants individually (NOT the average)
With two springs, does a mass oscillate at a higher or lower frequency?
Higher frequency because frequency increases with k in the equation: f = (1/2pi)*sqrt(k/m)
Does decreasing the length of a pendulum lead to an increase or decrease in period?
A shorter pendulum will have a shorter period because mass has to go through a smaller distance for a full cycle
What does decreasing the force of gravity do to the frequency of a pendulum?
Smaller frequency because mass will not be moving as fast because less force of gravity means less acceleration as well.
As a pendulum is shortened, what happens to the angle it makes with the vertical?
It increases because energy is still conserved and PE(max) is still the same so it still has to reach the same height, but since it is shorter, the angle/amplitude will increase in order to reach the same height
Does mass affect frequency and period?
Nope
What does increasing the tension in a cord fixed at both ends do the the frequency of the first harmonic generated?
It will increase the frequency because there will be less slack as it oscillates
If you increase period by 200%, what is the new period?
100% + 200% = 300%
What is the wavelength in terms of L for standing waves?
wavelength = 2/(nL)
What happens to frequency when you increase the mass on a spring?
Frequency will decrease
Does wave speed depend on the medium?
Yes
Can PE for a spring be negative?
No, it can never be negative because PE = 0.5kx^2 and k is never negative
Does mass matter for period and frequency in spring system or pendulum system?
Spring
Does changing the initial speed or displacement affect the frequency of a spring?
No, the frequency depends on the physical properties of the actual spring system, like the masses and the spring constant
If a marching band marches at the natural frequency of a bridge, what happens?
The bridge will resonate and this can cause the bridge to deteriorate faster
Increasing the beat frequency will lead to increase or decrease in number of beats in a given period?
Increase
