Question

Three balls are in water. Ball 1 floats, with half of it exposed above the water level. Ball 2, with a density less than the density of water is held below the surface by a cord anchored to the bottom of the container, so that it is fully submerged. Ball 3, of same radius as ball 2, but of greater mass, is suspended from a rope so that it is fully submerged.
Which is true for Ball 1? Choose the best answer.

1) The magnitude of the buoyancy force is exactly one half of that of the ball's weight.
2) The magnitude of the buoyancy force is more than that of the ball's weight.
3) The magnitude of the buoyancy force is less than that of the ball's weight.
4) The magnitude of the buoyancy force is equal to that of the ball's weight.

Answer 1

Answer:

4) The magnitude of the buoyancy force is equal to that of the ball's weight

Explanation:

Since ball 1 floats without sinking then it is in equilibrium. This means that the net downward force (weight) is balanced by the net upward force (buoyancy forces).

Answer 2

Answer:

The magnitude of buoyancy force is equal to that of ball's weight.

Explanation:

Ball 1 is floating on water. Weight of ball 1 is Fg=m1g  is acting vertically downward

Force of buoyancy FB = ρVdisg is acting vertically upward.

Net force acting on the ball is zero, FB=Fg

Answer

The magnitude of buoyancy force is equal to that of ball's weight.