The highest frequency humans can hear is about 20,000 Hz.

Introductory Chemistry 5
Classify each substance as a pure substance or a mixture. If it is a pure substance, classify it as an element or a compound. If it is a mixture, classify it as homogeneous or heterogeneous. (a) helium gas (b) clean air (c) rocky road ice cream (d) concrete

Introductory Chemistry 5
Is the melting of ice endothermic or exothermic? What is the sign of \(\Delta H\) for the melting of ice? For the freezing of water? Equation Transcription: Text Transcription: delta H

College Physics 1
Problem 25PE A projectile is launched at ground level with an initial speed of 50.0 m/s at an angle of 30.0 above the horizontal. It strikes a target above the ground 3.00 seconds later. What are the x and y distances from where the projectile was launched to where it lands?

Organic Chemistry 7
a. Which of the following has a nonpolar covalent bond? b. Which of the following has a bond closest to the ionic end of the bond spectrum? \(\mathrm{CH}_{3} \mathrm{NH}_{2}\) \(\mathrm{CH}_{3} \mathrm{CH}_{3}\) \(\mathrm{CH}_3\mathrm{F}\) \(\mathrm{CH}_{3} \mathrm{OH}\)

Sears and Zemansky's University Physics with Modern Physics 13
Problem 83P Visitors at an amusement park watch divers step off a platform 21.3 m (70 ft) above a pool of water. According to the announcer. the divers enter the water at a speed of 56 mi/h (25 m/s). Air resistance may be ignored. (a) Is the announcer correct in this claim? (b) Is it possible for a

Sears and Zemansky's University Physics with Modern Physics 13
Problem 21E If a photon of wavelength 0.04250 nm strikes a free electron and is scattered at an angle of 35.0 from its original direction, find (a) the change in the wavelength of this photon; (b) the wavelength of the scattered light; (c) the change in energy of the photon (is it a loss or a gain?

Chemistry for today : general, organic, and biochemistry 9
Refer to the group numbers of the periodic table and draw Lewis structures for atoms of the following: a. potassium b. barium c. aluminum d. bromine

Principles of Economics 9
Homer buys pizza for $10 and Pepsi for $2. He has income of $100. His budget constraint will shift inward if a. the price of pizza rises to $12. b. the price of Pepsi falls to $1. c. his income rises to $150. d. the price of pizza, the price of Pepsi, and his income all rise by 50 percent.