# Homework Help: Helicopter, velocity

1. Oct 8, 2015

### Drizzy

1. The problem statement, all variables and given/known data

A helicopter is hovering at a height of 10 meters. It weighs 6230 kg and the diameter of the rotos is 14.6 m. What is the speed of the air that the rotor is pushing down?

2. Relevant equations

How am I supposed to solve this problem?

3. The attempt at a solution

I'll probably need the area of the rotor but I haven't figured out why yet...

2. Oct 8, 2015

### stockzahn

With the diameter of the rotor you can calculate the size of the area, the air is pushed down to lift the helicopter.

3. Oct 8, 2015

### Drizzy

Why do I need the area? Maybe to calculate the mass of the air?

4. Oct 8, 2015

### stockzahn

Exactly. You have the possibilty to accelerate air with a small rotor to high velocities or with a large rotor to lower velocities to generate the force, that lifts the helicopter. With the area you can define which velocity you need the air speeded up.