Assuming the density of water is 62.4 lbm/ft3, and using standard gravity, how much does 1 gallon of water weigh?

The weight of the water is 37.14 N.

Explanation:

Given;

density of water, ρ = 62.4 lbm/ft³

volume of water, V = 1 gallon = 0.1338 ft³

The mass of the water is calculated as;

m = ρV

1 lbm = 0.454 kg

8.349 lbm = ?

= 3.79 kg

The weight of the water is calculated as;

W = mg

where;

g is acceleration due to gravity = 9.8 m/s²

W = (3.79)(9.8)

W = 37.14 N.

Therefore, the weight of the water is 37.14 N.

the velocity you are looking for is made up of two parts: horizontally velocity, vh, and its vertical velocity, vv. the actual velocity of the ball will be these two parts added together, and because velocity is a vector then they will need to be added vectorially.  

neglecting air resistance etc etc.,  

the horizontal velocity component will be constant (because there is no accelerating force in the horizontal direction.  

vh = 8 ms-1  

the vertical velocity component has an accelerating force: 'g'.  

using v = u +at where a = g = 9.81 ms-2.  

the vertical component of velocity, vv = 0 + gt = vv =9.81 x 2  

vv = 19.62 ms-1 . the zero appears because the virtical component of velocity at time t=0 is zero. remember, the ball was thrown horizontally.  

how fast it will be moving (it actual path (being a parabola )) will be the vector sum of these two.  

adding vectorally gives: -  

v = sqr root (8^2 + 19.62^2) = sqr root(64+384.9) = 21.18 or 21.2 ms-1