- #1

- 161

- 0

http://i14.photobucket.com/albums/a322/guitaristx/train.jpg

Heres what I came up with so far...

http://i14.photobucket.com/albums/a322/guitaristx/trainwork.jpg

I feel like Im missing some numbers....any suggestions?

- Thread starter Jason03
- Start date

- #1

- 161

- 0

http://i14.photobucket.com/albums/a322/guitaristx/train.jpg

Heres what I came up with so far...

http://i14.photobucket.com/albums/a322/guitaristx/trainwork.jpg

I feel like Im missing some numbers....any suggestions?

- #2

nrqed

Science Advisor

Homework Helper

Gold Member

- 3,736

- 279

Consider the situation when the train is just about to "fly off" and leave the tracks. In that case, the normal force on the train is zero. This should alllow you to solve for rho.

http://i14.photobucket.com/albums/a322/guitaristx/train.jpg

Heres what I came up with so far...

http://i14.photobucket.com/albums/a322/guitaristx/trainwork.jpg

I feel like Im missing some numbers....any suggestions?

EDIT: Question b does not make sense to me...What do they mean by "bottom of a hill"? Maybe we are to assume that we have now a track curved upward with the same radius?

- #3

- 161

- 0

A = N-g

A = 0 - 9.8m/s^2

so

r = 106^2/-9.8 = -1148 m

does that make sense for the first question?

- #4

nrqed

Science Advisor

Homework Helper

Gold Member

- 3,736

- 279

Well a radius can't be negative.

A = N-g

A = 0 - 9.8m/s^2

so

r = 106^2/-9.8 = -1148 m

does that make sense for the first question?

Be careful, you are using

[tex] \sum F_y = m a_y [/tex]

so your a_y should be [tex] - v^2/ r [/tex] not v^2/r.

Other than that it looks fine

- #5

- 161

- 0

how is Velocity negative when gravity is acting downward in the y direction?

- #6

- 161

- 0

- #7

nrqed

Science Advisor

Homework Helper

Gold Member

- 3,736

- 279

I never said that a velocity is negative. I am talking about the y component of the acceleration. The radial (or centripetal) acceleration a_rad always points to ward the center of the circle. In your example, the center of the circle is below the train. Thereforehow is Velocity negative when gravity is acting downward in the y direction?

[tex] a_y = - a_{Rad} = - \frac{v^2}{R} [/tex]

- #8

- 161

- 0

In terms of Normal and Tangential accerlation, when I draw the FBD if the normal Accerleration is upward, does that mean the Normal Force is also upwards?

- #9

nrqed

Science Advisor

Homework Helper

Gold Member

- 3,736

- 279

I am not sure what you mean by "normal acceleration". If we have circular motion, there is a radial accceleration and there is a tangential acceleration. The radial acceleration is toward the center of the circle. So downward in your diagram. The normal force is always perpendicualr and away from the surface so it's upward.

In terms of Normal and Tangential accerlation, when I draw the FBD if the normal Accerleration is upward, does that mean the Normal Force is also upwards?

- Replies
- 4

- Views
- 9K

- Replies
- 12

- Views
- 14K

- Replies
- 4

- Views
- 5K

- Last Post

- Replies
- 4

- Views
- 2K

- Replies
- 8

- Views
- 3K

- Last Post

- Replies
- 0

- Views
- 1K

- Last Post

- Replies
- 1

- Views
- 8K

- Replies
- 1

- Views
- 4K

- Replies
- 3

- Views
- 865

- Replies
- 1

- Views
- 2K