# Tension graph problem

1. Oct 11, 2005

### cheez

After drawing the graph, I still dun know how to solve the problem. I know I should use F=ma, but I really dun know about tension. btw, am I drawing the right sketch? thx so much!

2. May 25, 2009

### uskalu

Last edited: May 25, 2009
3. May 25, 2009

### DrDanger

I think the car is supposed to be going uphill; your car is going downhill..right?

4. May 25, 2009

### uskalu

nop it going up
thats why
F=m*a=friction+ tension+w*g*sin(theta) is upwards

5. May 26, 2009

### DorianG

Which direction is friction acting in?
I think you have it right in your picture, but you use it incorrectly when you're resolving forces in your equation.

6. May 26, 2009

### uskalu

since motion is upwards, the friction acts on downwards.

7. May 26, 2009

### PhanthomJay

I don't know who came up withthis problem or its solution, but it appears seriously flawed. Even if the 2nd car was on a level track, the brakes couldn't prevent it from sliding off the bridge along with the first car, if the coefficient of static friction was only 0.13. And then even assuming this is an incorrect coefficient, then in order to pull both cars up the slope, there would have to be a friction force up the slope, applied between the train's driving wheels and the tracks, to move it at some constant speed, not at some minimum acceleration, and the max force available would depend upon then mass of the car and the passengers in it. Bad problem.