Question

The luxury liner Queen Elizabeth 2 has a diesel-electric powerplant with a maximum power of 84 MW at a cruising speed of 35.0 knots. What forward force is exerted on the ship at this highest attainable speed

Answer 1

Answer:

$F = 4669.201\,kN$

Explanation:

Maximum speed is get at maximum power. Let assume that ship travels at constant speed, the expression for power is equal to:

$\dot W = F\cdot v$

Where $F$ and $v$ are the forward force and speed of ship measured in newtons and meters per second, respectively.

The forward force can be determined by clearing it in the expression described above:

$F = \frac{\dot W}{v}$

$F = \frac{84\times 10^{3}\,kW}{(35\,knots)\cdot \left(\frac{0.514\,\frac{m}{s} }{1\,knot} \right)}$

$F = 4669.201\,kN$

Answer 2

Answer:

F = 4.66×10⁶ N

Explanation:

Using,

P = F×vcosФ.............. Equation 1

Where P = maximum power of the plant, F = Forward force, v = cruising speed, Ф = angle between the force and the velocity.

At the maximum power, Ф = 0°

Therefore,

P = F×v

make F the subject of the equation

F = P/v..................... Equation 2

Given: P = 84 MW = 84×10⁶ W, 5=35 knots = (35×1.852) km/h = 64.82 km/h = 18.01 m/s.

Substitute into equation 2

F = 84×10⁶/18.01

F = 4.66×10⁶ N