Question

1. 1. The density of water is 1000 kg/m³. Compared to this, the density of air at sea level is

   		approximately 1000 times less.
   		approximately 100 times less.
   		approximately 10 times less.
   		about the same.

   
   

2. What is the gauge pressure at the bottom of a 5 feet deep swimming pool? (Answer in Pa)

3.You are given the task to determine the volume of an irregular shaped object. You hang it on a scale and measure its weight to be 34 N. When you submerge it in a bath of water, the scale reading changes to 15 N. What is the object's volume? (provide your answer in cm^3)

4.

1. You are given the task to determine the density of an irregular shaped object. You hang it on a scale. When you submerge it in a bath of water, the scale reading reduces to 67%. What is the object's density? (provide your answer in kg/m^3)

   
   
2. 5. You find a solid sphere of some unknown material. You determine its diameter to be 7.11 cm and its mass 0.627 kg. what is its density? (use kg/m^3 as units)
3. 
   

Answer 1

1)

the density of air = 1.225 Kg/m^3

which is approximately 1000 times less than water


2)


guage pressure in this care is the pressure excerted my the water above that point and neglecting the pressure do to atmospheric air

so guage pressure = rho * g * h

= 1000*9.81*(5*12*2.54/100)

= 14950.44 Pa



3)

the bouyant force exceted on the irregular body is the weight of liquid displaced by it

which is equal to the volume of the object * density of the liguid * acceleration due to gravity

density of liquid = 1000 Kg/m^3


so the buoyant force = weight in air - weight in water = 34 - 15 = 19 N

so 19 = v*1000*9.81

V = 1.936799*10^(-3) m^3

V=1936.799 cm^3


4)

let the mass in air be Mg

so

let the mass in water = 0.67Mg


so buoyant force = (Mg-0.67Mg) = 0.33Mg


this is equal to the weight of the liquid displaced

0.33Mg = V*1000*g

so M/V = density = 3030.3030 Kg/m^3



5)

volume of sphere = 4/3 * Pi*r*r*r


given diameter = 7.11 cm = 0.0711 m

radius = 0.03555 m


so volume = 4/3 * Pi * 0.03555^3 = 1.8819 * 10^(-4) m^3


given mass = 0.627 kg

so density = mass / volume = 0.627 kg / 1.8819 * 10^(-4) m^3 = 3331.655 Kg/m^3