Finding weight in Newtons?

Question

What is the weight of a column of water 7 ft high with a radius of 1.1m?
The density of the water is 1000 kg/m/m/m
Answer in units of N.


Volume = pi * r^2 * h
7 ft = 2.1336 m
Weight = Volume * Density


Volume = 3.14 * 1.1^2 * 2.1336 = 8.1064 m^3
Weight = 8.1064 m^3 * 1000 kg/m^3
Weight = 8106.39984 kg
1 Newton = kg * m/s2

i'm stuck here

Answer 1

You're nearly right, just you're confusing Mass with Weight.
Also, Density = MASS per unit Volume, not Weight

So MASS = Volume * Density
Mass = 8.1064 m^3 * 1000 kg/m^3 = 8106.39984 kg
Weight = Mass * g
where g=9.81 m/s²
Weight = 8106.4 * 9.81
= 79,520N

Answer 2

You need to get your definition straight, kilograms measures mass, not weight. The measure of weight is Newton=(kg*m)/(s^2). So, all you have to do is multiply what you got, that is, 8106.39984 kg( like i said which is just the mass) by 9.8 which the acceleration due to gravity, so your answer should be (8106.39984kg*9.8m/s^2), and as you can see the units are right.

For future reference: mass is measured in kilogram and is not the same thing as weight. To find the weight of anything on the earth, all you have to is multiply its mass(kg) by the accelaration due to gravity(9.8m/s^2).

Answer 3

Density, D = 1000 kg / m³
Volume, V = π (1.1)² (3.13) m³
V = 11.9 m³
Mass = D V
Mass = 11900 kg
F = Mg
F = 11900 x 10 N (taking g as 10 m/sec²)
F = 119000 N

Answer 4

http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html