Can Two Street Cars Be Pulled Up a Slope with a Low Friction Coefficient?

[cheez]

Two identical street cars are connected by a cable. One car has fallen off a bridge. The other car is going up a slope of 14 degrees, and has on its breaks, mu=0.13. People rush to jump on the second car so it will be heavy enough to pull up the first car. What is the initial acceleration of the cars, in ft/s^2

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? thanks so much!

 

[uskalu]

That's correct
goto http://knowhowstuff.blogspot.com/search/label/Physics%20Q%20and%20A
for more details

 

[DrDanger]

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

 

[uskalu]

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

 

[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.

 

[uskalu]

since motion is upwards, the friction acts on downwards.

 

[PhanthomJay]

since motion is upwards, the friction acts on downwards.

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.