Interactive Simulator · Equilibrium of three forces
The Washing-Line Surprise
A weight hangs from two strings that rise symmetrically to the supports. The object is in equilibrium, so the three forces (the weight and the two tensions) form a closed triangle. Slide the angle and watch the tension: the flatter the strings, the larger the tension, which is why a tightrope is never quite horizontal.
MissionLower the string angle toward horizontal and watch the tension. Predict the trend first.Streak 0Best 0
As the strings are made more horizontal (smaller angle), the tension in each string:
tension in each string T = W / (2 sinθ)7.8 N
vertical components 2T sinθ10.0 N
weight W10.0 N
In equilibrium the resultant is zero, so the three forces drawn nose to tail form a closed triangle. The two upward components add up to the weight.