# Homework Help: Spinning drum ride

1. Apr 24, 2010

### Alcape

1. The problem statement, all variables and given/known data
If a spinning drum ride cannot exceed a 10 m radius, and the riders are not to
experience an acceleration greater than 2g, what is the maximum speed at
which the drum can spin?

2. Relevant equations
No Idea

3. The attempt at a solution
I tried using (theta) = tan-1 of (rg/v2)
v2 = (tan(theta))/(rg)
v = (root) of (tan(theta))/(rg)

2. Apr 24, 2010

### tiny-tim

Hi Alcape!

(have a theta: θ )
What's θ? You can assume that the drum's wall are vertical.

Now use the standard formula for centripetal acceleration

3. Apr 24, 2010

### Alcape

If the walls are vertical then it doesn't work as it's at 90 degrees and tangent of 90 degrees then it comes out to be a mathematical error

4. Apr 24, 2010

### tiny-tim

ah … you obviously haven't seen one of these at a fairground.

Yes, if the walls are smooth, it can't be done, but you can assume the walls are rough, so that friction will keep you up (or even that there's a ledge to stand on ).

5. Apr 24, 2010

### Alcape

I now have the answer if you use the formula for acceleration:a=v2/r
and transpose it so that it becomes: v2 = a*r and therefore becomes:
v = √(a*r) and it comes out to be 4.47...

6. Apr 25, 2010

### tiny-tim

Hi Alcape!

(just got up :zzz: …)