How Do You Calculate the Force Exerted by Water in a Tank?

[lostinphysics44]

Homework Statement

An aquarium tank is 100 cm long, 35 cm wide, and 40 cm deep. It is filled to the top.
What is the force of the water on the bottom (100cmX35cm) of the tank?
What is the force of the water on the front window (100x40) of the tank?

Homework Equations

this where i am unsure is it just f=mg? or F=pA. how do i get p?

The Attempt at a Solution

tried the equations above and got nowhere. also tried to solve using the density of water to find the mass but got nowhere so please advise thanks.

 

[Astronuc]

how do i get p?

One needs to find the static head, P_h, which is given by

P_h = $\rho$ gh, where $\rho$ is the fluid density, g is the acceleration of gravity, and h is the height of the fluid.

http://hyperphysics.phy-astr.gsu.edu/hbase/pflu.html#fp