A 0.75 kg copper block (density 8900 kg/m³) hangs from a spring balance, fully under water.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A copper block (density ) hangs from a spring balance, fully under water. Find its volume, the buoyant force, and the reading of the balance. (.)
Need a reminder? The key ideaShow
Archimedes' principle: the buoyant force equals the weight of fluid pushed aside, . A body floats if it is less dense than the fluid, with the fraction of its volume under. Relative density .
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.
Step 1. Volume. .
Step 2. Buoyant force. .
Step 3. Reading. .
Answer: ; ; .
Check. The block loses of its weight, as its density says.
Watch out. The water's density, not the copper's, goes in the buoyant force.
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