a glass stopper suspended to the hook of a spring balance and immersed in water read 100gf. when a cork of volume 20 cc is tied to the glass stopper and then the combination is immersed in water , the reading of the spring balance will be:

a) more than 100gf

b) equal to 100gf

c) less than 100gf

d) none of the above

please explain also!

Cork being lighter than water will float on top its surface and thus the spring balance would experience a buoyant force form the water equal to its weight. The force exerted will be greater when an object is immersed. Thus, the reading of the spring balance will be less than the previous case- where the glass stopper was immersed in water.

Thus, correct answer is option (c).