January 22, 2017

Homework Help: physics

Posted by Benji on Monday, November 20, 2006 at 4:44pm.

A mass of 20 kg on a plane inclined at 40 degrees. A string attached to that mass goes up the plane, passed over a pullley and is attached to mass of 30 kg that hangs verticalyy. a) find the acceleration and it's dirction b) the tension in the string. Assume no friction.

I first drew the picture. How would I find the equation since F=ma doesn't include everything?

F=ma (combined with Newton's third law) give you all you need to solve this problem.

The force on the hanging mass in the downward direction is:

F2 = m2 * g - T

where m2 = 30 kg

The force on the other mass in the direction parallel to the plane in which the string is pulling is:

F1 = -m1 * g sin(40°) + T

where m1 = 20 kg

Begause the string is assumed to be of fixed length the acceleration of mass 1 in the direction the string is pulling must be the same as the acceleration of mass 2 in the downward direction.

This means that:

F1/m1 = F2/m2

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