Answer
a. 2 N.
b. 12 N.
c. 20 N.
Work Step by Step
a. The buoyant force is 10 N – 8 N = 2 N upward.
b. By Newton's third law, the rock pushes down on the liquid with a force of 2 N. The platform scale reads 2 N more than when the rock isn't suspended in the water.
c. The rock weighs 10 N, and the spring scale is no longer pulling up on it. The total weight on the platform scale is 20 N.
