PHYSICS · Single correct · AP · Physics 1: Algebra-based · Fluids · Fluids
Problem
A metal block is suspended from a spring scale. When the block is slowly lowered from air into a tank of water until it is completely submerged and at rest, the scale reading decreases. Which of the following best explains the decrease in the scale reading?
(a) The pressure on the top surface of the block becomes larger than the pressure on its bottom surface, producing a net downward force.
(b) The water exerts an upward force on the block equal to the weight of the water displaced by the block.
(c) When the block is immersed, the water exerts an upward force equal to the block’s own weight, so the scale reads less.
(d) The mass of the block effectively decreases when it is in water, so its actual weight becomes smaller.