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A lamp of weight 84 N hangs from two equal strings…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A lamp of weight hangs from two equal strings. Each string makes with the ceiling. What is the tension in each string?
Need a reminder? The key ideaShow
A body at rest is in equilibrium: the forces on it balance along every direction. Split each slanting force into parts:
A string pulls along its own length; a light string over a smooth nail has the same tension on both sides.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. ; each string at to the horizontal ceiling.
Plan. The horizontal parts cancel; the vertical parts hold the weight.
Step 1. Vertical balance. .
Step 2. Solve. .
Answer: Each string pulls with .
Check. Each tension, , is more than half the weight, , because the strings slant. If they hung straight down, each would carry exactly .
Watch out. Check whether the angle is given from the ceiling or from the vertical. It decides between and .
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