A diver descends from a salvage ship to the ocean floor at a depth of 35 m below the surface. The density of ocean water is 1.025x10^3 kg/m^3.
a) Calculate the guage pressure on the diver on the ocean floor.
b) Calculate the absolute pressure on the diver on the ocean floor.
The diver finda a rectangular aluminum plate having dimensions
1.0m x 2.0m x 0.03m. A hoisting cable is lowered from the ship and the diver connects it to the plate. The density of aluminum is 2.7x10^3 kg/m^3. Ignore the effects of viscosity.
c) Calculate the tension in the cable if it lifts the plate upward at a slow, constant velocity.
d) Will the tension in the hoisting cable increase, decrease, or remain the same if the plate accelerates upward at 0.05m/s^2? Justify your answer.
To get the pressure from the water weight, take a 1m^2 column of water of height given (35m). That gives you a volume of water, which can be converted to mass with the density.
Weight of the water= mass*g
Pressure on bottom of column is weight/1m^2
That is guage pressure. Now, absolute will add the atmospheric pressure at the top.
c. the tension on the cable will be weight of the aluminum minus bouyancy. Bouyancy will be the weight of water of the same volume as the aluminum.
d. Tension = weight-bouyancy + massaluminum*acceleration. Think about that.
would u know what formula i should use to get started on this?? and the fromulas for the problem
Yes, I do. I gave them in verbal form. Read what I wrote. I will be happy to critique your thinking.
ok for a im going to let e = roh...
so P = Po + egh
P=(1.025x10^3)(10)(35)
so my answer to a wiill be 358750??
P = Po + egh
P=(1.025x10^3)(10)(35)
density right, height right. What is the 10? Shouldnt it be 9.8? That gives the weight of the column of 1m^2, and dividing it by the area (1m^2) gives pressure in Pascals, normally, we write in kilopascals. Here is a rule of thumb to memorize: 33 feet (10 meters of water) equals barometric pressure, so 35 meters is about three times barometric pressure, which is just about what you have (baro pressure= 101kpa)
Good work.
yea my teacher makes us use 10 instead of 9.81 but for b) i just did
P = Po + egh
P = 1atm + 358750atm
so Pabs = 358751 atm ?????
and i am completely lost on c.. I know that tension = mg but i don't no how to find the mass of the aluminum.. they give me the volume right?
No. THe egh....and you need to do the units, is in Pascals. You cannot add pascals and atmospheres without changing one or the other. Practice putting units in your quantities, to see what comes out. Otherwise, you are blind to the units.
You may point out to your teacher, nicely, that nowhere on Earth is the acceleration due to gravity 10m/s^2.
Mass of aluminum is equalt to volume*density.
ok so my a is right but my b si wrong??
guage pressure is in pascals??
so what would my Patm be if I have
Patm = Po + 358750atm????
IM lost.. also for c i got the tension = 1620 and it increases for d.. it that right?
You may write pressure in any units you want, but you cannot add 1atm + xxxxpascals. the units have to be the same.
atmospheric pressure= 1atm= 101.3kPa
dont forget to include the boeyant force in your calculation for tension
dont forget to include the boeyant force in your calculation for tension
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