# Homework Help: Centripetal Force in an amusement park ride

1. Oct 27, 2008

### GoSS190

In an amusement park ride called The Roundup, passengers stand inside a 18.0 m-diameter rotating ring. After the ring has acquired sufficient speed, it tilts into a vertical plane. Suppose the ring rotates once every 4.90 s. and the rider's mass is 58.0 kg.

A.) With how much force does the ring push on her at the top of the ride?

B.) With how much force does the ring push on her at the bottom of the ride?

C.) What is the longest rotation period of the wheel that will prevent the riders from falling off at the top?

If anyone could help me with these questions that would be great. Thanks

I tried this using the equations to find v = (2pi(r)) / T

but then i realized that the velocity is different at the top than at the bottom. I am stumped as to how to find the velocity then find the force.

I think the equation for force at the top is (m(vtop)2) / R

Can anyone help me out with this though please

Last edited: Oct 27, 2008
2. Oct 27, 2008

### rock.freak667

At the top of the ring, what are the forces acting on the body? The resultant of those two forces is equal to the centripetal force.

3. Oct 27, 2008

### GoSS190

The two forces are the normal force and gravity but i dont know how to find the normal force

4. Oct 27, 2008

### rock.freak667

Yes, the are the two forces, the normal force (R) and the weight(W) <-I assumed that is what you meant by gravity.

The resultant of those two R+W=Fc where Fc is the centripetal force.

5. Oct 27, 2008

### GoSS190

How do you find the R or the normal force cause the velocity is different at the top than at the bottom

6. Oct 27, 2008

### rock.freak667

You don't need the velocity,the told you that "the ring rotates once every 4.90 s"

What does this tell you about the periodic time and hence the angular velocity?

7. Oct 27, 2008

### GoSS190

it would be 1 / 4.9 right

8. Oct 27, 2008

### rock.freak667

yes and how to relate that to angular velocity?

What formulas do you know to calculate centripetal force?

9. Oct 27, 2008

### GoSS190

2pi / 4.9 is the angular velocity

10. Oct 27, 2008

### rock.freak667

and centripetal force is therefore?

11. Oct 27, 2008

### GoSS190

That is the part that I dont understand really

12. Oct 27, 2008

### GoSS190

is it mw^2r

13. Oct 27, 2008

### rock.freak667

yes it is, you can now solve part a and part b noting that Weight acts downwards and normal reaction acts upwards

14. Oct 27, 2008

### GoSS190

i got an answer of 556177.07 but that doesnt seem correct to me and I dont know what i did wrong

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