Finding the Tension in a String Using Newton's Laws

AI Thread Summary
The discussion revolves around solving a physics problem using Newton's laws to find the tension in a string attached to a toy hanging from a van accelerating down a hill. The user successfully calculated the angle theta as 30.677 degrees by determining the van's acceleration and the downhill force. However, they are struggling to find the tension in the string and have attempted to use the equation F=ma without success. A suggestion was made to draw a force diagram to help visualize the forces at play. The user is seeking further guidance on how to approach finding the tension in the string.
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This problem involves Newton's laws. I got the first half of the problem but I am stuck on the second part. Please take your time to guide me through it, thanks!
Problem:
A van accelerates down a hill, going from rest to 30 m/s in 6 seconds. During the accceleration, a toy (m=.1kg) hangs by a string from the van's ceiling. The acceleration is such that the string remains perpendicular to the ceiling and to the ramp.

Determine a) the angle theta and b) the tension in the string.


Ok I found the angle theta by finding the acceleration of the van with the equation V=Vo+at. Next I found the downhill Force which is .5Newtons. Then I used F sub d(downhill force)=W sin theta. I came up with theta equals 30.677 degrees which is correct because I checked the answer.

How do I find the tension in the string? I tried using F=ma and came up with: F sub d + F sub y + (-T) = ma But that didn't work.. Fy is downward force perpendicular to the ramp, when I got x and y components.


Give me a hint for B) please! Thanks.
 
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the only thing that i can recommend is to draw a force diagram and label all the numbers on that and see if you can figure out some sort of equation from that
 
yeah I did.. but that's the equation I got and it doesn't work. :frown:
 
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