Periodic Motion and Waves

Question 1

Is the relationship between wavelength and frequency linear?

Answer 1

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

Question 2

If an object has changing speed, is kinetic energy conserved?

Answer 2

Nope

Question 3

If there is an external force acting on a pendulum, is momentum conserved?

Answer 3

Nope, external forces like gravity and tension do not conserve momentum

Question 4

If an object does not have conserved kinetic energy, can it still have conserved momentum?

Answer 4

No because if kinetic energy is not conserved like if speed keeps changing then that means momentum is changing too because p = mv

Question 5

How do you find tension when a pendulum is swinging through the lowest point?

Answer 5

F(tension) - F(gravity) = F(centripetal)

T - mg = (mv^2)/r

This is because the pendulum is swinging in the arc of a circle

Question 6

In a standing wave, where is the antinode?

Answer 6

It’s where the amplitudes are

Question 7

In a simple harmonic oscillation, where is kinetic energy and potential energy at there maximum?

Answer 7

Kinetic energy at maximum when it is at equilibrium.

Potential energy at maximum when it is at maximum amplitude.

Question 8

Are frequency and period dependent or independent of amplitude in SHO?

Answer 8

Independent

Question 9

As a mass moves from initial amplitude to equilibrium, what happens to the speed and acceleration?

Answer 9

Speed increases and acceleration decreases

Question 10

What is the equation for period of spring system?

Answer 10

T = 2pi* sqrt(m/k)

Question 11

What is the equation for period of pendulum system?

Answer 11

T = 2pi* sqrt(L/g)

Question 12

What are the units for spring constant (K)?

Answer 12

N/m or kg/s^2

Question 13

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?

Answer 13

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

Question 14

Where in a cycle of a pendulum is the kinetic energy equal to the potential energy?

Answer 14

Halfway between the KE max and PE max. So at t = pi/4, 3pi/4, 5pi/4, 7pi/4

Question 15

How are standing waves formed?

Answer 15

Waves of equal amplitude traveling in opposite directions

Question 16

Changing the mass on a horizontal spring will have what affect on KE and PE? What about speed? Assume same initial displacement.

Answer 16

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

Question 17

If a mass is attached at both ends of two springs, what is the PE at any point?

Answer 17

Because there are two springs, you add up PE from each individual spring so you get kx^2

Question 18

How does a heavier mass affect period of an oscillator?

Answer 18

It will increase period because heavier masses oscillate more slowly

Question 19

How does a stiffer spring, greater k, affect the period of an oscillator?

Answer 19

A stiffer spring will pull the mass back to equilibrium faster, so the period will be decreased

Question 20

With two springs, the effective spring constant is?

Answer 20

Doubled because you add up both spring constants individually (NOT the average)

Question 21

With two springs, does a mass oscillate at a higher or lower frequency?

Answer 21

Higher frequency because frequency increases with k in the equation: f = (1/2pi)*sqrt(k/m)

Question 22

Does decreasing the length of a pendulum lead to an increase or decrease in period?

Answer 22

A shorter pendulum will have a shorter period because mass has to go through a smaller distance for a full cycle

Question 23

What does decreasing the force of gravity do to the frequency of a pendulum?

Answer 23

Smaller frequency because mass will not be moving as fast because less force of gravity means less acceleration as well.

Question 24

As a pendulum is shortened, what happens to the angle it makes with the vertical?

Answer 24

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

Question 25

Does mass affect frequency and period?

Answer 25

Nope

Question 26

What does increasing the tension in a cord fixed at both ends do the the frequency of the first harmonic generated?

Answer 26

It will increase the frequency because there will be less slack as it oscillates

Question 27

If you increase period by 200%, what is the new period?

Answer 27

100% + 200% = 300%

Question 28

What is the wavelength in terms of L for standing waves?

Answer 28

wavelength = 2/(nL)

Question 29

What happens to frequency when you increase the mass on a spring?

Answer 29

Frequency will decrease

Question 30

Does wave speed depend on the medium?

Answer 30

Yes

Question 31

Can PE for a spring be negative?

Answer 31

No, it can never be negative because PE = 0.5kx^2 and k is never negative

Question 32

Does mass matter for period and frequency in spring system or pendulum system?

Answer 32

Spring

Question 33

Does changing the initial speed or displacement affect the frequency of a spring?

Answer 33

No, the frequency depends on the physical properties of the actual spring system, like the masses and the spring constant

Question 34

If a marching band marches at the natural frequency of a bridge, what happens?

Answer 34

The bridge will resonate and this can cause the bridge to deteriorate faster

Question 35

Increasing the beat frequency will lead to increase or decrease in number of beats in a given period?

Answer 35

Increase