A piece of metal of volume 250 cetimetre cube floats in water when 85 percent of it's volume is under water.Calculate the upthrust on the metal.
250*85=21250
well, 250*0.85 = 212.5 cm^3
so it displaces
212.5 grams of water assuming water has density of 1 gram/cm^3
If your book does force in grams, that is the answer.
However that 212.5 grams is really the MASS of water displaced. To get the force up you really should multiply that by g, the acceleration of gravity which would give you force in dynes. g = 981 cm/s^2 on earth approximately
This is the second question in a row which confused mass and weight or force. Are you using the same old physics book I wonder?
Our spring scales would not work on the moon correctly. We would have to multiply the measurement in grams or kilograms by 6 to get the right answer :)
On the other hand a balance scale would work fine.
Surely one can't have a book that old, the binding would be brittle.
To calculate the upthrust on the metal, we need to first find the volume of water that is displaced by the metal. Since 85% of the metal's volume is under water, we can calculate the volume of water displaced by multiplying the metal's volume by 85% (0.85).
Metal's volume = 250 cm^3
Volume of water displaced = 250 cm^3 * 0.85 = 212.5 cm^3
Now, we can calculate the upthrust on the metal using Archimedes' principle, which states that the upthrust or buoyant force acting on an object submerged in a fluid is equal to the weight of the fluid it displaces.
The density of water is approximately 1 g/cm^3, so the mass of water displaced by the metal can be calculated as follows:
Mass of water displaced = Volume of water displaced * Density of water
= 212.5 cm^3 * 1 g/cm^3 = 212.5 g
Finally, we can find the upthrust using the formula:
Upthrust = Mass of water displaced * Acceleration due to gravity
Acceleration due to gravity is approximately 9.8 m/s^2. Since the mass is in grams, we need to convert it to kilograms before calculating the upthrust.
Upthrust = 212.5 g * (1 kg / 1000 g) * 9.8 m/s^2
= 2.08 N
Therefore, the upthrust on the metal is approximately 2.08 Newtons.