The problem says:
"A record rainstorm produced 304.8 mm (approximately 1 ft)
of rain in 42 min. Estimate the average force that the rain exerted
on the roof of a house that measures 10 m * 16 m. Indicate
any assumptions you made. (Note: density of water is 1000 kg/m3"
The Attempt at a Solution
I determined the mass of the rain that fell in the 42 minute/2520 second interval to be 48,768kg and the mass of rain to fall in one second to be 19.35kg.
From there I am absolutely at a loss of what to do to figure out the average force. Assuming that the final velocity of the rain is 0, I'm thinking that I need the initial velocity of the rain in order to figure out the change in momentum.
The answer itself isn't a problem, as I was given a key, but I'm not sure if I should use the mass of all of the rain and 2520 seconds as Δt or use 19.35kg and 1 second as Δt. I'm just really not sure where to go after calculating the masses of the amounts of rain.
The key says the answer is 2x10-4 N, but I can't figure out how to get to that answer.