- #1

- 22

- 3

## Homework Statement

A 200 lb man lies against the cushion on a Rotor ride, which is inclined at θ=10°. The coefficient of static friction is μs=0.3. Radius is 8 ft. Find minimum speed so that the man does not slip down.

## Homework Equations

ΣF

_{n}= ma

_{n}

ΣF

_{z}= 0

a

_{n}= v

^{2}/r

## The Attempt at a Solution

OK, so I've done several of these problems without any issues. But now I'm running into a problem finding minimum velocity.

Here's my setup:

ΣF

_{n}= mv

^{2}/r

FnormalCos80-0.3FnormalCos10 = 6.21v

^{2}/8

ΣF

_{z}= 0

FnormalSin80+0.3FnormalSin10 = 200

The positive z axis is up, and the positive n axis is to the left.

The issue is that once I plug the normal force into my first equation, the left hand side becomes negative. This is the same approach I've taken with other problems, but with larger angles. I feel like I'm going insane. Can someone please help me out? Thanks.