Why do sound waves need a medium through which to travel?

If you travel from Yakima to Ellensburg (Yakima to Ellensburg is 50 miles) with a speed of 60 miles/hour for half of the trip and 80 miles/hour the other half of the trip. What is your Average speed? HINT: It is not 70 miles/hour:

Explain how magnetic forces enable a maglev train to float above the tracks. Magnetic forces use two main components to keep a maglev train afloat.

Use the particle model to draw a motion diagram for a bike rider riding at a constant pace. Use the lowercase "o" on the keyboard to represent the particle.

A circuit contains two resistors connected in parallel. The value of R1 is 2,000 and the value of R2 is 4,200. What is the total resistance in this circuit? A. 2,709 B. 6,200 C. 1,355 D. 987

The change in internal energy during one complete cycle of a heat engine A. equals the net heat flow into the engine. B. equals zero. C. equals the heat energy exhausted from the engine. D. equals the heat energy entering the engine.

Which of these is the best reason for proper nutrition? A. To ensure that you will be skinny B. To protect yourself against certain diseases C. To improve your intelligence D. To ensure that you will get good grades

And object has a mass of 15g it has a volume of 7.5ml. find the density of the object.

I need this answered quickly. is the branch of science for naming and classifying organisms based on their natural relationships? A-physics B-taxonomy C-genetics D-biology

For a fixed amount of gas, if the absolute temperature of the gas is doubled, what happens to the pressure of the gas?

A 500-kilogram sports car accelerates uni- formly from rest, reaching a speed of 30 me- ters per second in 6 seconds. What distance has the car traveled during the 6 seconds?