a 100 kg boulder is placed under the surface of water. its volume is 0.5 x 10^5 cm^3. what is the weight of the rock while under water; compare that to the weight of the rock in air (sitting on the ground)
i just found the weight of the rock in air by multiplying 100 kg by 9.8 and got 980 kg. but i don't know what to do next
No. The question is what is the weight of the rock as compared to in air.
The weight of the rock under water is
Wuw= mg-volume*densitywater*g
The weight of the rock in air is mg
comparing them..
wuw/Wair= (mg-volume*densitywater*g)/mg
= 1-volume*densitywater/m)
but m is volume*densityrock
Wuw/Wair= 1-densitywater/densityrock
check that math
To find the weight of the rock while under water, you need to consider the buoyant force acting on the rock. The buoyant force is the upward force exerted by a fluid, in this case, water, on an object immersed in it.
To calculate the weight of the rock under water, you can use Archimedes' principle, which states that the buoyant force on an object is equal to the weight of the fluid it displaces. Here's how you can find the weight of the rock under water:
1. Determine the volume of water displaced by the rock. The given volume of the rock is 0.5 x 10^5 cm^3, which represents the volume of the rock itself. We need to find the volume of water displaced by the rock, which is equal to its own volume.
2. Convert the volume from cm^3 to liters. Since 1 liter is equal to 1000 cm^3, divide the given volume by 1000 to get the volume in liters.
3. Multiply the volume in liters by the density of water. The density of water is approximately 1000 kg/m^3 or 1 g/cm^3. Multiplying the volume in liters by the density of water will give you the mass of the water displaced by the rock.
4. Convert the mass of the water displaced to kilograms if needed.
5. Subtract the mass of the water displaced from the weight of the rock in air to find the weight of the rock under water. The weight of the rock under water will be less than the weight of the rock in air because it experiences a buoyant force.
By following these steps, you can calculate the weight of the rock while under water.