The diagram below shows a person using a device called a jetpack. Water is forced downwards from the jetpack and produces an upward force on the person. State the condition necessary for the person to be able to remain stationary in mid-air.

The condition that's necessary for the person to be able to remain stationary in mid-air is thrust.

Thrust is the force that propels, forces, or pushes the mass of an object in a particular direction. Thrust is the propulsive force of a rocket engine or a jet.

Based on the diagram, it can be inferred that water is the fuel that is used in propelling the user upward. Therefore, the condition that's necessary for the person to be able to remain stationary in mid-air is thrust.

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The condition necessary for the person to be able to remain stationary in mid-air is that there must be an upward force also referred to as THRUST

Explanation:

Thrust in Physics is defined as the force that propels, forces or pushes the mass of a certain object in a specified or particular direction.

Thrust can defined in the terms of a Jet pack can be defined as the force that is required to propel the mass of a person in an upward direction.

Based on the diagram that we have been shown the question, we can see that water is the fuel used to proper the user or person upwards hence, the jet pack used in the question is an HydroJet pack

The condition necessary for the person to be able to remain stationary in mid-air is that the propelling force called the thrust must be upwards such that it can overcome these 4 things:

a) Gravitational force

b) Mass of the jet pack user

c) Mass of the jet pack itself

d) The water which serves as fuel for the jet pack.