Tovi is playing a flute and Dawn is playing a violin. At the beginning of the performance, they tuned their instruments by ear, so the difference between the fundamental frequencies of the A notes played on each instrument was less than 1 Hz. At the end of the performance, they measured the A note fundamental frequencies of their instruments using a device that measures sound frequencies with uncertainty 0.05 Hz. Dawn's frequency was 442.6 Hz and Tovi's was 439.3 Hz. (a) Can you say for sure that the A note frequency of at least one musical instrument changed during the performance? (b) Can you say for sure that the A note frequency of both musical instruments changed during the performance? (c) What do Dawn and Tovi hear when they simultaneously play the A note at the end of the performance? Give a quantitative description.

Explain the difference between validity and reliability.

Simplify each expression. Assume that all variables are positive when they appear. $9 \sqrt[3]{24}-\sqrt[3]{81}$

$$\dfrac{4}{5}-\left(-\dfrac{3}{10}\right)$$

Two monocular depth cues are most responsible for our ability to know that a jet flying overhead is at an elevation of several miles. One cue is relative size. What is the other? a. Relative motion. b. Retinal disparity. c. Interposition. d. Light and shadow. e. Linear perspective.

A boat is moving up and down in the ocean with a period of $1.7 \mathrm{s}$ caused by a wave traveling at a speed of $4.0 \mathrm{m} / \mathrm{s}$. What other physical quantities relevant to this wave can you determine using this information? Determine them.

Solve each equation. a. $5x-7=2x+2$ b. $3g-8=5g-20$ c. $1-3b=2b-8$ d. $15-4k=12-7k$

The sound intensity $5 \mathrm{km}$ from the place where a supersonic jet takes off is $0.60 \mathrm{W} / \mathrm{m}^{2}$.Determine the area of a sound collector you would need to run a $40-W$ lightbulb from the energy collected. What might require you to create a larger collector?

Use an organized list or a tree diagram to identify the possible arrangements for a) the ways that three friends, Jo, Amy, and Mike, can arrange themselves in a row. b) the ways that you can arrange the digits 2, 5, 8, and 9 to form two-digit numbers. c) the ways that a customer can choose a starter, a main course, and a dessert from the following menu.

LUNCH SPECIAL MENU Starter: soup or salad Main: chili or hamburger or chicken or fish Dessert: ice cream or fruit salad

What conditions are necessary to create a sinusoidal wave in a certain medium? What is needed to create a wave of a different frequency? Different speed? Different wavelength?

Write an absolute value inequality that represents the set of numbers. All real numbers at most 6 units from 0.

In what kind of star system does one star block the light from another? a. open cluster b. binary star system c. quasar system d. eclipsing binary

One end of a horizontal string of length L passes over a pulley with a block hanging at the end. A motor attached to the other end of the string exerts a constant horizontal force on the string. When the motor is turned on, it vibrates the end of the string up and down at frequencies that increase slowly from zero to a high frequency. What do you observe?

The sound intensity at a gasoline station next to a freeway averages $10^{-3} \mathrm{W} / \mathrm{m}^{2}$.The owner decides to collect this energy and convert it to thermal energy for heating his building. Assuming that this conversion is $100 \%$ efficient, what is the length of one side of a square sound collector that is needed to provide ther mal energy at a rate of $500 \mathrm{W}$? Is this a practical idea for the owner? Explain.