Transcript Chapter 13

Springs
• Hooke’s Law (Fs)
FS  kx
• Spring Constant (k)
• Spring Force – is a restoring force
because it always pushes or pulls towards
the equilibrium position.
Simple Harmonic Motion
• Simple harmonic motion occurs when the
net force along the direction of motion
obeys Hooke’s Law
– In other words, when the net force is
proportional to the displacement from the
equilibrium point and is always directed
towards the equilibrium point.
Fig. 15.3, p.456
Terminology
• Amplitude (A) – maximum displacement
• Period (T) – time it takes the object to
move through one complete cycle
• Frequency (f) – the number of complete
cycles per unit of time
1
f 
T
• Acceleration (a) ma  F  kx
k
a x
m
The Equations
Equations of Motion
for the object-spring system
Pendulum Equations
Types of Traveling Waves
• Transverse wave – the displacement of
the wave is perpendicular to the motion of
the wave
– Sine and cosine graphs
– Light waves (electromagnetic waves)
• Longitudinal wave – the displacement of
the wave is parallel to the motion of the
wave
– Sound waves
Fig. 16.2, p.488
Fig. 16.5, p.489
Fig. 16.3, p.488
Fig. 16.10, p.495
Terminology and Equations
• Wavelength (l)
• Wave speed (v)
v
l
T
 fl
• Mass per unit length (m)
m
m
l
• If the wave is traveling on a string then the
wave velocity is defined as:
T
v
m
Fig. 16.8a, p.492
IMPORTANT
• There are two different velocities for a
traveling transverse wave.
– The wave speed, which is literally how fast
the wave is moving to the left or to the right.
– The transverse velocity, which is how fast
the wave (rope, string) is moving up and
down.
Wave Interference
• Superposition Principle – when two or
more waves encounter each other while
traveling through a medium, the resultant
wave is found by adding together the
displacements of the individual waves
point by point.
Fig. 18.1, p.545
Fig. 18.2, p.546