Help it's a physics question?

Question

There is a 3.7 mass on a frictionless inclined surface and is connected to a 2kg mass. The pulley has no mass or friction. The 2kg mass is acted upon by an upward force of 3.9N, and a downward acceleration of 4.6m/s^2. I found the tension in the connecting string and it was 6.5N what I don't get is how to find the angle please help me with this someone else tried and they did 4.6=gsin, but that was wrong and I don't think the other person is going to answer. Please help me.

Answer 1

Your question is a little unclear. I think you are saying that an upwards force of 3.9 N acts on the 2 kg mass, which is suspended vertically of the top ledge of the incline, and the masses are accelerating at 4.6 m/s^2.

So, let's draw a free body diagram and show all the forces acting on the two blocks. Of course, I can't actually draw it; you'll have to do it in accordance with my description. Draw the two masses horizontally, connected by a line, the string between them. For this FBD, forget about the fact that they are not oriented in a straight line. Draw the 2 kg mass to the left of the 3.7 kg mass. (Or the other way around if you like, but then you'll have to reverse all of my other directions.) The gravitational force acting on the 2 kg mass will be mg = (2 kg)(9.8 m/s^2) = 19.6 N, and this acts towards the left. The 3.9 N force acting upwards on the 2 kg mass now acts to the right in this orientation. Finally, the force of gravity on the 3.7 kg mass in the direction of the incline will be mg*sin(theta) = (3.7 kg)(9.8 m/s^2)*sin(theta) = (36.26 N)*sin(theta), where theta is the unknown angle of the incline, and it acts to the right.

So you've got three forces acting on these masses: a force of gravity to the left, a force of gravity to the right, and an applied force to the right. The acceleration, 4.6 m/s^2, is towards the left in this case. If you sum up the forces, you'll get sum(F) = ma. Assume that the right is the positive direction. Then (-19.6 N) + (3.9 N) + (36.26 N)*sin(theta) = ((3.7 kg) + (2 kg))*(-4.6 m/s^2), and theta is your only unknown.