DAY 63

*After some deep introspection, I decided that the Mass on a Spring Interactive assignment will now be extra credit. Turn it in by Thursday for some bonus lab points*

Unit Goals: What is a wave? How do they act? How are do waves differ?

Goals: SWBAT...

1. Define Amplitude & Wavelength

2. Find the Compression and Rarefaction zones on a longitudinal wave

3. Use Period and Frequency correctly to solve problems

Warm-Up (5min):

1. Sketch the image. From where to where could you measure the wavelength? (hint, there are at least 4 answers)

CLASSWORK

1. #063A: Wave Components

Transverse Waves (like in the warm up)

a. Amplitude: distance from rest to crest

b. Wavelength: length of one complete wave cycle (peak to peak, or trough to trough)

Longitudinal Waves

a. Compressions: where the waves are tightly packed (or compressed)

b. Rarefactions: where the wave are spread apart (or rare)

c. From where to where could you measure wavelength in the longitudinal wave above?

Check Your Understanding

Consider the diagram below in order to answer questions #1-2.

1. The wavelength of the wave in the diagram above is given by letter ______.

2. The amplitude of the wave in the diagram above is given by letter _____.

3. Indicate the interval that represents one full wavelength.

a. A to C

b. B to D

c. A to G

d. C to G

#063B: Frequency & Period

a. if I say, "How frequently do you mow the lawn during the summer months?" what I'm really saying is, ____ _____ do you mow the lawn

b. TERM: Frequency

DEFINITION: In mathematical terms, the frequency is the number of complete vibrational cycles of a medium per a given amount of time.

UNITS: cycles/second, waves/second, vibrations/second, or something/second Hz is the most common unit, which is called Hertz, and means cycles/second

SYMBOL: f (for frequency)

c. TERM: Period

DEFINITION: The time it takes to complete one cycle (ex: time it takes for one wave to go by, time for one class from start to finish)

UNITS: any time unit, but usually

SYMBOL: T (For time, but not little t, cause that's also time. Easy, right?)

d. How Are They Related?

Frequency is the cycles/second. Period is the seconds/cycle. Is there are relationship here? Could you come up with an equation?

063C: Practice Problems:

1. A wave is introduced into a thin wire held tight at each end. It has an amplitude of 3.8 cm, a frequency of 51.2 Hz and a distance from a crest to the neighboring trough of 12.8 cm. Determine the period of such a wave.

2. Frieda the fly flaps its wings back and forth 121 times each second. The period of the wing flapping is ____ sec.

3. A tennis coach paces back and forth along the sideline 10 times in 2 minutes. The frequency of her pacing is ________ Hz.

4. Non-digital clocks (which are becoming more rare) have a second hand that rotates around in a regular and repeating fashion. The frequency of rotation of a second hand on a clock is _______ Hz.

5. Olive Udadi accompanies her father to the park for an afternoon of fun. While there, she hops on the swing and begins a motion characterized by a complete back-and-forth cycle every 2 seconds. The frequency of swing is _________.

6. In problem #5, the period of swing is __________.

7. A period of 5.0 seconds corresponds to a frequency of ________ Hertz.

8. A common physics lab involves the study of the oscillations of a pendulum. If a pendulum makes 33 complete back-and-forth cycles of vibration in 11 seconds, then its period is ______.

9. A child in a swing makes one complete back and forth motion in 3.2 seconds. This statement provides information about the child's

a. speed

b. frequency

c. period

10. The period of the sound wave produced by a 440 Hertz tuning fork is ___________.

11. As the frequency of a wave increases, the period of the wave ___________.

a. decreases

b. increases

c. remains the same

Stuck? Answers are here at the bottom of the page: LINK

At Home Learning (HW)

1. Complete #63C