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### HW 1.39

Posted: Tue Apr 17, 2018 6:15 pm
Not sure which topic to put this under:

39) A baseball must weigh between 5.00 and 5.25 ounces (1 ounce 28.3 g). What is the wavelength of a 5.15-ounce baseball thrown at 92 mph?

How would you go about solving something like this? Not sure which equation I should be using.

### Re: HW 1.39  [ENDORSED]

Posted: Tue Apr 17, 2018 7:55 pm
I would think you would use wavelength= h/mv. Where h= plancks constant (Js), m=mass (g), v= velocity (m/s). At first convert ounces to grams and mph to m/s, then I would use the equation mentioned.

### Re: HW 1.39

Posted: Wed Apr 18, 2018 11:16 pm
I solved the problem and a key thing to remember is that 1 Joule= 1kg x m^2 x s^-2

### Re: HW 1.39

Posted: Thu Apr 19, 2018 6:08 pm
Yes, you would use the equation lambda=h/mv, and make sure to convert the given values into SI units.

### Re: HW 1.39

Posted: Fri Apr 20, 2018 2:28 pm
Exactly, as stated above, the correct units should be used. But nobody said the correct units, but only alluded to it. So, yea, in solving a De Broglie's equation, using kg for the mass is important for 1 J = 1kg*(m^2)*(s^-2)

### Re: HW 1.39

Posted: Fri Apr 20, 2018 6:54 pm
The way I went about this is just noticed what values we are given. We are given mass and velocity (which must first be converted to kg and m/s of course). I then knew that we must use de Broglie's equation, which gives us the wavelength of any particle. We then solve for wavelength using the equation and we notice that the wavelength is sooooo small that it an undetectable wavelength, which makes sense since we are talking about a baseball instead of a particle and thus quantum mechanics do not apply (in other words big things we can see do not have wavelengths). Hope that helps.

### Re: HW 1.39

Posted: Fri Apr 20, 2018 9:17 pm
You would need to use DeBroglie's Equation (wavelength= h/(mass x velocity))

1) Convert 5.15 ounces to grams (which will be the mass to plug into the equation)

2) Convert mph to meters per second (which will be the velocity to plug into the equation)

3) Plug in all converted variables into Debroglie's equation and you should get 1.1 x10^-34 as your answer :)

### Re: HW 1.39

Posted: Sun Apr 22, 2018 1:11 pm
Just a really quick follow up question. When I was looking up at solutions online in order to make sure that I was getting the correct answer I noticed that some solutions said the MPH meant meters per hour while others said it was miles per hour. I was pretty sure MPH was miles per hour, but I just wanted to check and make sure I was doing the problem correctly. So what does MPH mean in this question?

### Re: HW 1.39

Posted: Sun Apr 22, 2018 2:45 pm
MPH is miles per hour