Question

(1596) Discuss (with free-body diagrams) how a jet ski accelerates, brakes and turns.

Answer 1

A) the jet ski accelerates by sucking in the water and ejecting it with a higher speed from its back portion. The engine works as a modified centrifugal pump. When water ejects from the engine in the back then Newton's 3rd law dictates that the reaction force puts the jet ski into acceleration.

0 Forward force (free body diagram)

B) As the water is ejecting from the back from a steel pipe, the exit pipe can be moved in a horizontal plane to left or right. This thrust creates a moment about the center of mass of the boat and the boat turns accordingly.

Direction of turning Direction of Direction of thrust Direction of thrust Direction of water iet Direction of water jet

C) The brake system is controlled by part of the manuvering system called deflectors. This is roughly a hemispherical shaped pard which deflects the water to the front to create a backward thrust which stops the moving ski.

Force towards the front of boat