Choose any 3 of the following 4 questions to answer. If you answer more than 3,
ID: 1390734 • Letter: C
Question
Choose any 3 of the following 4 questions to answer. If you answer more than 3, your best Scores will be used and the remaining one discarded. 1.A man of mass m = 75.0 kg and an average density of p = 1.030 kg/m^3 (while holding his breath) is completely submerged in water. A) What is the buoyant force on the man? B) What is the acceleration of the man as he sinks I the water (neglect any viscous dreg from the water)? C) If he were to release the air from his lungs (about 5 L, 1 L = 1,000 cm^3) how would the answers of the previous 2 parts change (describe the effects, do not try to calculate the numbers)? D)After he hits the bottom (5 m down) what is the gauge pressure felt by the man?Explanation / Answer
A) The buoyant force equals the weight of the volume of water that the man occupies, this is:
mass(of the man)/density: 0.07m3.
The density of the water is 1000Kg/m3.
The mass of the equivalent volume of water is 1000Kg/m3*0.07m3=70Kg
The force over the man is F=mw*g=686N
B) You may ignore the effect of the pressure of water above the man in the moment he enters the water. Applying Newton's 2nd Law to the man.
mm.g-Fb=mm.a
Solving for "a", a=0.65m/s
C) In part "A", the buoyant forces decreases, because he had an internal extra buoyant force due the air.
In part "B" the acceleration increases it's value, since it's inversely proportional to the buoyant force.