Chapter 13 Flashcards
(16 cards)
What is hooke’s law?
Force entered by an ideal spring
When a strong is stretched or compressed a small distance from its unstretched or equilibrium position, the spring exerts a force that is proportional to the amount of stretch or compression but opposite to the direction
THIS DOESN’T APPLY JUST TO SPRINGS, APPLIES TO ANY SYSTEM IN WHICH THERE IS A POSITION OF STABLE EQUILIBRIUM AND A FORCE WHISE MAGNITUDE IS PROPORTIONAL TO AND OPPOSITE THE DISPLACEMENT FROM EQUILIBRIUM
Fs=-kx
Slides 5-7 Jan 17
What is simple harmonic motion?
How do you find acceleration?
If the magnitude of the restoring force is directly proportional to the displacement from the equilibrium position
SHM results
Slide 11-12 Jan 17
Force causing SHM is F=-kx
Acceleration
a(max)= -k/m (A)
What is frequency and time/period in simple harmonic motion?
Frequency is the number of oscillations per unit time (1/s)
Period is the time for one complete oscillation or cycle of motion
f=1/T in Hz (1/s)
What is the net force acting on an object in simple harmonic motion?
How would you go about finding velocity?
The net force is equal to the conservative elastic force due to the spring
Slide 17-18 Jan 17
V= square root (k/m) x square root (A^2-x^2)
How does simple harmonic motion compare to uniform circular motion?
How do you find velocity for this?
The shadow of uniform circular motion is in simple harmonic motion
V=-Vo/A square root(A^2-x^2)
Slide 20-22 Jan 17
How do you find position as a function of time?
X=ACos(2πft) IN RADIANS
slide 27-31 Jan 17
What is the motion of a pendulum? (Force of tension
Ft=-mgSinθ Ft=-mgSin(S/L) If the angle is small (θ<15), Ft=-mg(s/L) ****Ft=-(mg/L)s*** Form of F=-kx
Slide 7 Jan 22
How do you find the period for any pendulum?
T=2π square root(I/mgL)
Period never relies on mass
What are the 3 types of damped oscillations?
Real oscillators have frictional forces, energy loss, decreasing amplitude
Under damping- some oscillations still occur before the system comes to rest
Critical damping- the system returns to rest in the minimum amount of time
Over damping- no oscillations occur and the displacement slowly decreases to zero as the system comes to rest
Slide 18 Jan 22
What is a wave?
Wave is a motion of disturbance
All waves carry energy and momentum, but matter is not transported
Mechanical waves require a source of disturbance, medium that can be disturbed, connection or mechanism through which portions of the medium can affect each other
What are the 3 types of waves?
Transverse- disturbance is perpendicular to motion of wave (wave on a string)
Longitudinal- medium is duplicated parallel to the direction of wave motion (sound wave)
Soliton- solitary wave front that propagates without dissipating energy or dispersing
Simple harmonic oscillator produces a harmonic wave (every point in medium moves in simple harmonic motion at same frequency as the wave source
Slide 22 Jan 22
How do you find the speed of waves on springs?
Two motions occur in a string that carry a wave:
- motion of disturbance which moved at constant wave speed, λf
- the simple harmonic motion of individual pieces of the string, that move at a changing speed, v=-ωASin(ωt)
Is the wave speed the same as the speed of a particle in the wave medium?
No
For a uniform medium the wave speed is constant
Particle in the medium moves up and down with a speed that is different than the wave speed that is not constant
What is the superposition principle?
When 2 or more travelling waves encounter eachother while moving through a medium, resultant wave is found by adding the displacements of each wave point by point
Only valid for small amplitude waves
Slide 21-27 Jan 24
What happens with a wave reflected at a fixed end?
Closed or hard boundary
Newton’s 3rd law, attachment point pulling down on the string results in an inversion of the pulse reflected back
Partly reflected and partly transmitted
Slide 30 Jan 24
What happens when a wave is reflected at a free end?
Open or soft boundary Free end is displaced upward more than any other part of the spring Reflected pulse is not inverted Partly transmitted and partly reflected Slide 32 Jan 24
