Hard Phys Science Questions Need Help

[wigz]

im so confused on this!

[wigz]

anyone?

[CraigD]

It'd be best for you to post your attempts at answering these questions, along with specific questions your have about each one. Otherwise, we'd either be giving overly vague advice, or simply doing your homework for you.

[wigz]

this was my attempt ... its due tom at 9 am so any help will be great.. thanks

[CraigD]

Your first try is pretty good, wigz. :thumbs_up Here are some corrections and advice:

 

Problem 1: “17150” is a correct answer, in meters, but you didn’t write any units, and your work doesn’t make much sense.

 

With a simplifying assumption, this problem requires only that you know the definition of speed, which is the equation:

speed = distance / time

So if you’re given the values of two of the three terms, you can calculate the third.

 

You’ve been given a time (50 seconds), and implicitly, a speed (since you detected the blast’s “noise”, it’s the speed of sound at a standard temperature of 20C).

 

Look up the speed of sound, write the speed equation, solve it for distance, and you’re done.

 

Can you say what the simplifying assumption is? (Hint: it involves the speed of light)

 

Problem 3: You looked like you were on the right track, but made a simple arithmetic mistake and a type. Your work should be neater, starting with the definition you’re using, and working to the answer of the question.

 

For this problem, you need to know the definition of frequency and wavelength, which is the equation:

Frequency = speed / wavelength = wavecount / time

 

Take just the part you need (speed / wavelength = wavecount / time). You’ve been given count, time, and wavelength, so write rewrite the equation and solve for speed, and you’re done.

 

Hints: 10/3 is NOT 10.3; and the unit of speed in this problem is m/s, not n/s.

 

Problem 4: The key to this problem is knowing that frequency is the same for a sound wave in different mediums (think about it – if it wasn’t, waves would have to get lost or found in the different mediums). So for this problem, you use

Frequency = speed / wavelength

again, but here you have 2 different speeds and one give wavelength, so you need to combine it with itself to get:

speed_water / wavelength_water = Frequency = speed_air / wavelength_air

 

You’ve been given the value of one of the terms, and you can look up the others, (you can take out “frequency”, and just write it:

speed_water / wavelength_water = speed_air / wavelength_air

), so rewrite and solve for wavelength_water, and you’re done.

 

Problem 5: Your answer is right, but you might not get full credit, because you explanation is kinda sketchy. Here’s where you need to use the equation for approximate speed of sound in air given temperature it looks like you wrote in problem 1,

Speed of sound in air = 331.3 +0.606*Temperature m/s/C

to explain that the speed of sound decreases as temperature decreases, then the definition of speed,

Speed = distance / time

to explain that, when speed decreases and distance stays the same, time increases.