Diffraction Applications Physics 202 Professor Lee Carkner Lecture 26.
Waves Physics 202 Professor Lee Carkner Lecture 5.
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Transcript of Waves Physics 202 Professor Lee Carkner Lecture 5.
PAL #4 Pendulums The initial kinetic energy is just the
kinetic energy of the bullet
The initial velocity of the block comes from the kinetic energy KE = ½mv2
Amplitude =xm, can get from total energy
Initial KE = max KE = total E = ½kxm
xm =(2E/k)½ = ([(2)(1250)]/(5000))½ = 0.71 m Equation of motion = x(t) = xmcos(t)
k = m2
x(t) = 0.71 cos(31.6t)
Test Next Friday About 15 multiple choice
Like Quizdom About 4 problems
Like PALs or homework Bring calculator and pencil Formulas and constants provided (but not
labeled) Worth 10% of grade I have put practice problems on webassign
Not for grade
Waves Properties
The wave has a net displacement but the medium does not
The y position is a function of both time and x position and can be represented as:
y(x,t) = ym sin (kx-t) Where:
k = angular wave number = angular frequency
Wavelength and Number
One wavelength must include a maximum and a minimum and cross the x-axis twice
We will often refer to the angular wave number k,
k=
Period and Frequency
Frequency is the number of oscillations (wavelengths) per second (f=1/T)
=2/T
The quantity (kx-t) is called the phase of the wave
Speed of a Wave
y(x,t) = ym sin (kx-t) But we want to know how fast the waveform moves
along the x axis:v=dx/dt
If we wish to discuss the wave form (not the
medium) then y = constant and: kx-t = constant
we want to know how fast the peak moves
Velocity
k(dx/dt) - = 0(dx/dt) = /k = v
Since = 2f and k = v = /k = 2f/2
v = f
i.e. v is the velocity of the wave form
If the amplitude of a linear oscillator is doubled, what happens to the period?
a) Quarteredb) Halvedc) Stays the samed) Doublede) Quadrupled
If the amplitude of a linear oscillator is doubled, what happens to the spring constant?
a) Quarteredb) Halvedc) Stays the samed) Doublede) Quadrupled
If the amplitude of a linear oscillator is doubled, what happens to the total energy?
a) Quarteredb) Halvedc) Stays the samed) Doublede) Quadrupled
If the amplitude of a linear oscillator is doubled, what happens to the maximum velocity?
a) Quarteredb) Halvedc) Stays the samed) Doublede) Quadrupled
If the amplitude of a linear oscillator is doubled, what happens to the maximum acceleration?
a) Quarteredb) Halvedc) Stays the samed) Doublede) Quadrupled
If you have a pendulum of fixed mass and length and you increase the length of the path the mass travels, what happens to the period?
a) Increaseb) Decreasec) Stay the same
If you have a pendulum of fixed mass and length and you increase the length of the path the mass travels, what happens to the maximum velocity?
a) Increaseb) Decreasec) Stay the same