A 5.2 kg box is on a frictionless 36 degree slope and is connected via a mass less string over a mass less, frictionless pulley to a hanging 2.1 kg weight.

Question

What is the tension in the string if the 5.2 kg box is held in place, so that it cannot move?

Answer 1

If the 5.2 kg box is not moving, neither is the 2.1 kg weight.

The weight's weight of 2.1 * 9.8 = 20.6 N is balanced by the string tension.