Another Wheel Problem

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mathdad

mathdad

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How many feet does a wheel with a radius of 16 inches travel after 4 hours?

Solution:

I know the circumference must be found.
However, I notice that the radius is given here not the diameter.

Let d = diameter

Let r = radius

d = 2r

d = 2(16 inches)

d = 32 inches

C = pi(32 inches)(4 hours)

Is this the correct set up?
 
If the wheel has 0 angular velocity it's going to travel 0 feet in any amount of time.
You need to specify the angular velocity of the wheel for this problem to make any sense.
 
Romsek said:
If the wheel has 0 angular velocity it's going to travel 0 feet in any amount of time.
You need to specify the angular velocity of the wheel for this problem to make any sense.
Click to expand...

The problem is worded as stated at algebra.com.
 
Ah- that's a different matter- though it is still not complete! A wheel with 16 inches radius has circumference \(\displaystyle 32\pi\) inches so after 4 revolutions will have gone \(\displaystyle 128\pi\) inches. At 4 revolutions per hour it will have gone \(\displaystyle 128\pi\) inches or \(\displaystyle \frac{32}{3}\pi\) feet in one hour. To calculate a distance you have to specify both speed and time. In your original problem you did not specify a speed. Here you do not specify a time.[/tex][/tex]
 
HallsofIvy said:
Ah- that's a different matter- though it is still not complete! A wheel with 16 inches radius has circumference \(\displaystyle 32\pi\) inches so after 4 revolutions will have gone \(\displaystyle 128\pi\) inches. At 4 revolutions per hour it will have gone \(\displaystyle 128\pi\) inches or \(\displaystyle \frac{32}{3}\pi\) feet in one hour. To calculate a distance you have to specify both speed and time. In your original problem you did not specify a speed. Here you do not specify a time.[/tex][/tex]
Click to expand...

Sorry but the problem is as posted at algebra.com.
 
mathdad said:
Let d = diameter

Let r = radius

d = 2r

d = 2(16 inches)

d = 32 inches

C = pi(32 inches)(4 hours)
Click to expand...
(I realize the problem of the units has been fixed but this needs to be said.)

You are doing a Physics problem here and there's something you need to check every time you do a calculation: Do the units match?

On the LHS we have a circumference measured in "inches."

On the RHS we have the unit "inches-hours."

Clearly the units do not match so the answer is incorrect.

-Dan
 
topsquark said:
(I realize the problem of the units has been fixed but this needs to be said.)

You are doing a Physics problem here and there's something you need to check every time you do a calculation: Do the units match?

On the LHS we have a circumference measured in "inches."

On the RHS we have the unit "inches-hours."

Clearly the units do not match so the answer is incorrect.

-Dan
Click to expand...

This problem comes from an algebra site not a physics site. The units of physics are not required. I will go back check algebra.com just to make sure the wording is correct.
 
Mathdad, there you go again questioning the advise of one of the volunteers.
You know that the circumference of a circle is C = d*pi, but you say that equal d*pi*time. That MUST be wrong because the units don't match.
 
Jomo said:
Mathdad, there you go again questioning the advise of one of the volunteers.
You know that the circumference of a circle is C = d*pi, but you say that equal d*pi*time. That MUST be wrong because the units don't match.
Click to expand...

I know what the problem is with me. I am not retarded. I am posting TOO MANY questions, TOO MANY math topics at the same time. This ends today. I will stick to one topic at a time with less questions, of course.
 
mathdad said:
I know what the problem is with me. I am not retarded. I am posting TOO MANY questions, TOO MANY math topics at the same time. This ends today. I will stick to one topic at a time with less questions, of course.
Click to expand...
No one is saying that. I'm certainly not. (Though I will say again that I think you are overloading yourself.)

However I'm afraid that you are completely wrong about the units: I don't care where you got the problem, if you are working with units then the units on both sides of the equation must match. (When units are involved we are automatically taking a step away from pure Math to some kind of Science.)

-Dan
 
topsquark said:
No one is saying that. I'm certainly not. (Though I will say again that I think you are overloading yourself.)

However I'm afraid that you are completely wrong about the units: I don't care where you got the problem, if you are working with units then the units on both sides of the equation must match. (When units are involved we are automatically taking a step away from pure Math to some kind of Science.)

-Dan
Click to expand...

Can you give me a sample question?
 
mathdad said:
The problem is worded as stated at algebra.com.
Click to expand...
Except that is not true, is it?

We ask that you state the "exercise completely and accurately." The reason is that a student's difficulty frequently comes from paraphrasing the problem incorrectly. In this case, you were told that the information provided was insufficient and then wasted your and everyone else's time disputing that statement
 
JeffM said:
Except that is not true, is it?

We ask that you state the "exercise completely and accurately." The reason is that a student's difficulty frequently comes from paraphrasing the problem incorrectly. In this case, you were told that the information provided was insufficient and then wasted your and everyone else's time disputing that statement
Click to expand...

I stated the truth. Check out algebra.com. I have no reason to lie, to waste your time and mine. Moving on.
 
JeffM said:
Except that is not true, is it?

We ask that you state the "exercise completely and accurately." The reason is that a student's difficulty frequently comes from paraphrasing the problem incorrectly. In this case, you were told that the information provided was insufficient and then wasted your and everyone else's time disputing that statement
Click to expand...
I suspect - this student's problem stems from the fact that he is not using paper and pencil before typing out a response (90% of the mobile phone users do not have enough time or patience to use paper and pencil).
 
I did a google-search with: "How many feet does a wheel with a radius of 16 inches travel after 4 hours? "

No problem was found.

I did another google-search with: "How many feet does a wheel "

I got a hit at algebra. com (https://www.algebra.com/algebra/hom...metry_Word_Problems.faq.question.1066319.html ) with the following problem:

How many feet does a wheel with a diameter of 18 inches travel after three revolutions? Round to two decimal places as needed.

Mathdad - where is your problem?
 
Subhotosh Khan said:
I did a google-search with: "How many feet does a wheel with a radius of 16 inches travel after 4 hours? "

No problem was found.

I did another google-search with: "How many feet does a wheel "

I got a hit at algebra. com (https://www.algebra.com/algebra/hom...metry_Word_Problems.faq.question.1066319.html ) with the following problem:

How many feet does a wheel with a diameter of 18 inches travel after three revolutions? Round to two decimal places as needed.

Mathdad - where is your problem?
Click to expand...
https://www.algebra.com/algebra/hom...metry_Word_Problems.faq.question.1041315.html
 
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