# Circular Motion - Wall of death Problem

1. Apr 5, 2008

### blackbird2552

1. The problem statement, all variables and given/known data

Total mass = 260 kg
Coefficient of Friction = 1.00
r = 4 m
gmax = 4 g

a) Find the minimum speed to keep the rider on the wall of death.

b) Find the maximum speed inside the wall of death of the motorcycle based on gmax

2. Relevant equations

$$\mu$$ x (mv^2/r) = mg
Fc = mv^2/r
Gforce = mv^2/r

3. The attempt at a solution

a)

V = $$\sqrt{ g r / \mu}$$

V = 6.26 m/s

b)

Gforce = mv2/r

4 = 0.26g x v2 / 4 m
V = 7.84 m/s

I dont know if it is right...

2. Apr 5, 2008

### Andrew Mason

Correct.

I can't follow your reasoning. What is the maximum radial (normal to the wall) force (in Newtons)? What is the relationship between that force and the speed of the motorcycle? What is the motorcycle speed needed to achieve that force?

AM

3. Apr 5, 2008

### blackbird2552

..what i need to do is find is the maximum speed at which the motorcycle should be going to get the max value of g, that is 4 gs....i don't get how i will calculate it!....what i did is, since Fc = mv^2/r....the gforce = mv^2/r., i had the mass and the radius...i solved it for v....i think i should convert the 4 g to the force in newton that would be the maximum radial (normal to the wall) force (in Newtons)...i don't know how to do that...help?...

4. Apr 6, 2008

### blackbird2552

i think i got where i went wrong in the second one

The total force acting when the mass is experiencing 4 gs is

4g = 39.24 m/s2
F = ma
F = 260 kg x 39.24 m/s2 = 10202.4 N

to get the max v

Fc = mv2/r

10202.4 = 260kg x v2 / 4 m
V = underoot 156.96
V = 12.5 m/s

Is this right??...

5. Apr 6, 2008

Correct.

AM