# How do vehicles vertically take off or land?

Jul 2, 2018

To take off or land vertically the vehicle's weight must be counteracted with an opposing force upwards.

#### Explanation:

To take off or land vertically the vehicle's weight (downwards force due to gravity) must be counteracted with an opposing force upwards (acting through the centre of mass).

• If the opposing force is directly opposite and greater than the downwards force then the vehicle will move straight upwards.

• If the opposing force is directly opposite and less than the downwards force then the vehicle will move straight downwards.

• If the 2 forces are equal and opposite then the vehicle will be stationary (hover).

• If the 2 forces are not in exactly opposite directions then the vehicle will accelerate horizontally as well.

Helicopters generate the lifting force with a rotating wing (main rotor). This displaces enough air mass at high enough acceleration to create the force needed.

$\text{Force" = "mass" xx "acceleration}$

VTOL jets use powerful jets of exhaust gas directed downwards.

VTOL drones use multiple rotors to create multiple upwards forces that combine to make the required upwards force.

Any force due to wind must also be exactly opposed if the vehicle is to move only vertically.