Barron's 2nd Edition PT1 Q24

Barron's Book

24) The problem asks us tor find the tension in the string. If the mass m is held stationary, the net force must be 0. Our first step would be to draw a free body diagram for all forces.

Where m is mass, F[g] is gravitaional force, T is tension force, and F[N] is normal force

Since tension force is parallel to the incline, and since the normal force is perpendicular to the incline, we will put the gravitational force in components parallel and perpendicular to the incline.

This means there must be a component of gravity that equates to the tension force and a component that equates to the normal force.

Where m is mass, F[g] is gravitaional force, T is tension force, and F[N] is normal force

Finally, all we need to do is sum the forces that are parallel to the incline. Keep in mind that the object is stationary, so the net force should be 0.

Where F[Net] is net force, F[g] is gravitational force, m is mass, g is acceleration of gravity, and T is tension force

Answer: B