Question

The rotor blades of a helicopter propel 2500kg of air vertically downwards every second. The air, initially at rest, is accelerated to a speed of 15 m/s. If the helicopter starts to rise with an acceleration of 12.5 m/s, what is the mass of the helicopter?

Answer 1

Question #69141, Physics / Classical Mechanics

The rotor blades of a helicopter propel 2500kg of air vertically downwards every second. The air, initially at rest, is accelerated to a speed of 15 m/s. If the helicopter starts to rise with an acceleration of 12.5 m/s, what is the mass of the helicopter?

Solution

$$m = \frac{F}{a};$$ $$F = \frac{\Delta p}{\Delta t} = \frac{m \Delta v}{\Delta t};$$ $$F = \frac{2500 \times 15}{1} = 37500 \text{ N}$$ $$m = \frac{37500}{12.5} = 3000 \text{ kg}$$

Answer: 3000 kg.

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