**Problem 9:** The engine of a JF-Thunder fighter develops a thurst of 3000 N. What horsepower does it at a velocity of 600 m/s.

**Solution**

Thurst is the force that acts on the plane to move it forward as a result of the hot air it emits. Power is the dot product of force (thurst in this case) and velocity. Now the force and velocity are in the same direction, therefore, θ = 0.

P = Fvcosθ . Put the values,

P = 3000 × 600 × 1 = 1800000 watt

Now the watt-hp conversion is

746 watts = 1 hp OR 1 watt = (1/746) hp

Multiply both sides by 1800000, we have,

1800000 watts = (1800000/746) hp

1800000 watts = **2413 hp
(Answer)**

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