If a rainstorm drops 5 cm of rain over an area of 13 km2 in the period of 3 hours, what is the momentum (in kg · m/s) of the rain that falls in five seconds? Assume the terminal velocity of a raindrop is 10 m/s. (Enter the magnitude. The density of water is 1,000 kg/m3.)

Respuesta :

To solve the problem it is necessary to apply the concepts related to Conservation of linear Moment.

The expression that defines the linear momentum is expressed as

P=mv

Where,

m=mass

v= velocity

According to our data we have to

v=10m/s

d=0.05m

[tex]A=13*10^6m^2[/tex]

Volume [tex](V) = A*d = (15*10^6)(0.03) = 3.9*10^5m^3[/tex]

t = 3hours=10800s

[tex]\rho = 1000kg/m^3[/tex]

From the given data we can calculate the volume of rain for 5 seconds

[tex]V' = \frac{V}{t}*\Delta t_{total}[/tex]

Where,

[tex]\Delta t_{total}[/tex] It is the period of time we want to calculate total rainfall, that is

[tex]V' = \frac{3.9*10^5}{10800}*5[/tex]

[tex]V' = 1.805*10^2m^3[/tex]

Through water density we can now calculate the mass that fell during the 5 seconds:

[tex]m' = V'*\rho[/tex]

[tex]m' = 1.805*10^2*1000[/tex]

[tex]m' = 1.805*10^5m^2[/tex]

Now applying the prevailing equation given we have to

[tex]P=m'v[/tex]

[tex]P = (1.805*10^5)(10)[/tex]

[tex]P = 1.805*10^6 Kg.m/s[/tex]

Therefore the momentum of the rain that falls in five seconds is [tex]1.805*10^6 Kg.m/s[/tex]