Force exerted on a seat on rollercoaster

[annamae]

Homework Statement

We have a general rollercoaster design- a hill and a perfect circle loop,
the hill is 55m high and the loop has a radius of 20m. What is the force exerted on the passenger seat at the very top of the loop?
a. 300
b. 500
c. 750
d. 1000
e. 0

Homework Equations

a_c=v²/r
Fnet=Fg+Fn+Fp+Ff

The Attempt at a Solution

I found centripetal acceleration to be 15 m/s²
The velocity is 17.32 m/s
Fnet= 60(9.8)+60(15)
But my final answer is 1500N which isn't one of the above choices
So what am i doing wrong?

 

[zush]

How did you get that velocity? since v=(2gh)^0.5, you get v=32.833 m/s. Also, what's the mass of the roller-coaster?

 

[PhanthomJay]

How did you get that velocity? since v=(2gh)^0.5, you get v=32.833 m/s.

No, use conservation of energy between the top of the hill and the top of the loop to find v

Also, what's the mass of the roller-coaster?

Looks like it's 60 kg, from the OP's calc..which was left out of the problem statement.

Homework Statement

We have a general rollercoaster design- a hill and a perfect circle loop,
the hill is 55m high and the loop has a radius of 20m. What is the force exerted on the passenger seat at the very top of the loop?
a. 300
b. 500
c. 750
d. 1000
e. 0

Homework Equations

a_c=v²/r
Fnet=Fg+Fn+Fp+Ff

The Attempt at a Solution

I found centripetal acceleration to be 15 m/s²

Yes, how did you arrive at this?

The velocity is 17.32 m/s

yes,how did you arrive at this?

Fnet= 60(9.8)+60(15)

No, Fnet = Fg + Fn, you have written Fnet = Fg + ma

But my final answer is 1500N which isn't one of the above choices
So what am i doing wrong?

Fnet = Fg + Fn = mv²/r, solve for Fn, which is what the problem is asking.