1. Unit 4: Oscillatory Motion and Mechanical Waves

2. Terms: Oscillation: a repetitive back and forth motion
Cycle: one complete oscillation
Period (T): time for one complete oscillation
Frequency ( f ): number of oscillations per second.

3. Simple Harmonic Motion
Repetitive back and forth motion
Hooke’s Law
Force varies directly with displacement
Equilibrium position: spring is neither compressed or expanded.
Spring Constant (k): spring stiffness (N/m)
Slope of a F vs. x graph is the spring constant

4. Restoring Force:
Force that moves the object back to its equilibrium position.
Always acts in a direction opposite to the displacement
When representing the restoring force:

5. Horizontal SHM Amplitude: maximum displacement.
At max displacement, the restoring force is at maximum
When the mass is let go, the mass will accelerate towards the equilibrium position. ( F = ma)
As the mass moves through the equilibrium position, it will slow down.

6. Vertical SHM
Mass will come to rest when Fg is equal to the upward pull of the spring (at equilibrium)

7. Example:
An spring has a spring constant of 40.0 N/m. This spring is pulled with a force of 85.0 N to the left. What is the extension?

8. Example:
A 675 g mass is hung vertically from a spring. If the spring has a constant of 15.0 N/m, how far was the spring stretched?

9. Homework:
Page 347 #7, 9-12
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