Buoyant force?

Question

A swimmer wears a heavy belt to make her average density exactly equal to the density of water. Her mass, including the belt, is 55 kg.
(a) What is the swimmer's weight in newtons? (total weight, including belt)
_____ N
(b) What is the swimmer's volume in m^3?
_____m^3
(c) At a depth of 2 m below the surface of a pond, what buoyant force acts on the swimmer?
______N
What net force acts on her?
_____N

Answer 1

a) 55 * 9.8 = 539
b) d = m/v. solve for v = m/d. so m = 55kg, d= 1000kg/m^3; so v = 55kg/(1000kg/m^3) = 0.055m^3
c) 539 N; its the same as the weight of the person in N.
d) the net force is 0 N. since the person is in equilibrium.

Answer 2

> (a) What is the swimmer's weight in newtons? (total weight, including belt)

Weight = m × g. They tell you how much "m" is; and "g" is just the acceleration due to gravity (9.8m/s²).

> (b) What is the swimmer's volume in m^3?
_____m^3

volume = (average density) × (mass). They tell you how much her average density and her mass are. Multiply.

> (c) At a depth of 2 m below the surface of a pond, what buoyant force acts on the swimmer?
______N

Buoyant force = Weight of displaced water.

The "Displaced water" is the amount of water that equals the swimmer's volume. How much does that amount of water weigh? (Hint: the swimmer and the water both have the same density. How much does the _swimmer_ weigh?)

> What net force acts on her?

Net force = (weight) − (buoyant force).