Physics - Force on towed trailer

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KindofSlow

Junior Member
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Mar 5, 2010
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Hello,
I hope it is ok to post a physics problem here.
Q: A 1,280-kg car pulls a 350-kg trailer. The car exerts a horizontal force of 3,600-N against the ground in order to accelerate. What force does the car exert on the trailer? Assume an effective friction coefficient of 0.15 for the trailer.
Normal force on trailer is 9.8*350=3,430-N. So the force of Friction is -0.15*3430= -514.5-N.
I am stuck here without knowing either the magnitude of the acceleration or the coefficient of friction for the car.
Any guidance as to what I am missing will be greatly appreciated.
Thank you
 
KindofSlow said:
Hello,
I hope it is ok to post a physics problem here.
Q: A 1,280-kg car pulls a 350-kg trailer. The car exerts a horizontal force of 3,600-N against the ground in order to accelerate. What force does the car exert on the trailer? Assume an effective friction coefficient of 0.15 for the trailer.
Normal force on trailer is 9.8*350=3,430-N. So the force of Friction is -0.15*3430= -514.5-N.
I am stuck here without knowing either the magnitude of the acceleration or the coefficient of friction for the car.
Any guidance as to what I am missing will be greatly appreciated.
Thank you
Click to expand...

Start with drawing free-body-diagrams of the car, trailer and car+trailer. Assume the required force is T and the acceleration of the system is A.

Then for the car:



3600 - T = 1280*A .................................................................(1)

for the trailer:

T - 514.5 = 380 * A...............................................................(2)

Solve for T and A.

Remember to draw your FBDs. If I were the instructor, 60% of the credit will be assigned to drawing correct FBDs.
 
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