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