Magnitude and Direction Problem

[shorti2406]

These magnitude and direction problems always give me a really hard time! What other numbers should I have in order to solve this problem? Hopefully from that I will be able to figure out the proper equation to use. Thanks!


Q: A roller coaster car of mass 320 kg (including passengers) travels around a horizontal curve of radius 30 m. Its speed is 18 m/s. What is the magnitude and direction of the total force exerted on the car by the track?

 

[scholzie]

Uniform Circular Motion.
$$F=\frac{mv^2}{R}$$.

You already know m, v, and r, so there are no other numbers you need to know. F is the centripetal force needed to keep the car on the track. Look in your book to find out the direction of the accelleration of the car, and you have your answer.

 

[shorti2406]

I keep getting the answer 3456 N. But it keeps coming out wrong. What am I not doing correctly?

 

[scholzie]

I keep getting the answer 3456 N. But it keeps coming out wrong. What am I not doing correctly?

Is the correct answer 4667 N at 42 degrees? If so, you're missing a force. If not, I'm missing something too.

 

[Norman]

I agree with scholzie. The trick is remembering ALL the forces the track is exerting on the rollercoaster car.

 

[shorti2406]

That is the right answer. I am not sure how you got that though. I guess I'll just have to keep working at it! Thanks for all your help!

 

[Norman]

So if I have this same rollercoaster car not moving around the curve what forces are acting on it? Will these forces disappear when the car starts moving? Remember that forces are vectors.

 

[scholzie]

That is the right answer. I am not sure how you got that though. I guess I'll just have to keep working at it! Thanks for all your help!

Say, would this roller coaster happen to be in outer space? I assume it's on Earth...

Draw a free-body diagram with all of the forces acting on it.