find the density of a 5kg cylinder that is 10cm tall and has a radius of 3cm?

Question

calculate the height of the water column in a water barometer, assuming an atmospheric pressure of 10 (raised to the 5 power) Pa.

what would be the final temperature when 100g of 25degC water is mixed with 75g of 40degC water?
CALUCLATIONS PLEASE!!!

Answer 1

1. density = mass/volume
volume of a cylinder = l*pi*r^2
where l is length, r radius

2. a Pascal is a Nt/m^2 so you have a pressure of 100,000 Nt on an area of 1 m^2.
Water has a density of 1000 kg/m^3. So consider a column 1 m tall, with a base with an area of 1 m^2. It has a mass of 1000 kg. And a weight of m*g = 9,800 Nt.

You need a column of water tall enough to provide a weight of 100,000 on an area of 1 m^2. So you need the height to be
100,000/9,800 times the height of the column you considered in the paragraph above.

3. Both quantities of water will change to a new temp T. The cooler water will gain a certain amount of heat. The warmer water will loose the same amount of heat.

m1*c*(T-25) = m2*c*(40-T)