Answer:
20 N
Explanation:
In air, the normal force is equal to the weight.
∑F = ma
N − mg = 0
N = mg
Submerged in water, the normal force is equal to the weight minus the buoyant force:
∑F = ma
B + N − mg = 0
N = mg − B
Plugging in values:
80 N = 100 N − B
B = 20 N
