Consider a ship of mass 2 x 10^6 kg with propeller blades of radius 7 m and it can push water backwards to a speed of 2 m/s. Given that the density of water is 1000 kg/m^3 , find the acceleration of the ship. (required answer is 0.308 m/s)

Respuesta :

Answer:

[tex]a = 0.308 m/s^2[/tex]

Explanation:

As we know that the force due to propeller when it will push the water backwards is given as

[tex]F = \frac{dP}{dt}[/tex]

now we know that

[tex]P = mv[/tex]

so we have

[tex]F = v\frac{dm}{dt}[/tex]

[tex]F = v \rhoA\frac{dx}{dt}[/tex]

[tex]F = \rho A v^2[/tex]

here we know that

[tex]A = \pi r^2[/tex]

[tex]A = \pi(7^2)[/tex]

[tex]A = 154 m^2[/tex]

now the force is given as

[tex]F = (1000)(154)(2^2)[/tex]

[tex]F = 616000 N[/tex]

now the acceleration of the ship is given by Newton's II law

[tex]a = \frac{F}{m}[/tex]

[tex]a = \frac{616000}{2 \times 10^6}[/tex]

[tex]a = 0.308 m/s^2[/tex]