# TrigonometrySpeed of a Bicycle

#### karush

##### Well-known member
The tires of a bicycle have radius of $13 \text{ in}$ and are turning at a rate of
$\displaystyle\frac{200\text{ rev}}{\text{min}}$

How fast is the bicycle traveling in
$\displaystyle\frac{\text{mi}}{\text{hr}}$

well my try on this is.

$\displaystyle 26\pi\text{ in } \cdot \frac{200\text{ rev}}{\text {min}} \cdot \frac{\text {ft}}{12\text{ in}} \cdot \frac{\text {mi}}{5280\text{ ft}} \cdot \frac{60\text { min}}{\text{ hr}} \approx\frac{15.5\text { mi}}{\text{ hr}}$
no answer given so hope this is it.. assume "rev" not a unit measure but doesn't cancel out so its not carried thru..

#### Klaas van Aarsen

##### MHB Seeker
Staff member
Re: speed of a Bicycle

The tires of a bicycle have radius of $13 \text{ in}$ and are turning at a rate of
$\displaystyle\frac{200\text{ rev}}{\text{min}}$

How fast is the bicycle traveling in
$\displaystyle\frac{\text{mi}}{\text{hr}}$

well my try on this is.

$\displaystyle 26\pi\text{ in } \cdot \frac{200\text{ rev}}{\text {min}} \cdot \frac{\text {ft}}{12\text{ in}} \cdot \frac{\text {mi}}{5280\text{ ft}} \cdot \frac{60\text { min}}{\text{ hr}} \approx\frac{15.5\text { mi}}{\text{ hr}}$
no answer given so hope this is it.. assume "rev" not a unit measure but doesn't cancel out so its not carried thru..
Yep. That is it.
And indeed, "rev" is not a unit measure - it's dimensionless.
Or if you want, you have $2\pi \cdot 13 \text{ in/rev}$, making it cancel out nicely.

#### karush

##### Well-known member
Re: speed of a Bicycle

Yep. That is it.
And indeed, "rev" is not a unit measure - it's dimensionless.
Or if you want, you have $2\pi \cdot 13 \text{ in/rev}$, making it cancel out nicely.
cool tip..

I am going to start another thread with one that is to me. I don't understand RAD...