Question

A gymnast is preparing their dismount from the high bar. Once they let go of the bar, they will attempt to complete two complete twists coupled with a double backflip prior to landing. 1) This motion is occurring in two planes, about two axes.Identify which plane, and about which axis, each component of the rotation is occurring. 2) To generate the proper takeoff velocity and remain in the air long enough to complete the rotations, the gymnast must let go of the bar in a fully extended position. However, in this position, the gymnast will not rotate quickly enough to complete the dismount and land in an upright position. Discuss the principle of conservation of angular momentum, and how this principle can be used to alter the velocity of rotation. What are some things the gymnast can do to increase the speed of rotation about each axis.

No pictures needed just a conceptual question.

Answer 1

1) First, they are going to do two complete twists, these twists. These twists are about an axis, this axis lies in a vertical plane.

Then a double backflip before landing. This double backflip is about an axis, this axis lies in a horizontal plane.

2) The most important thing for the gymnast here is to do quick twists and backflips to be able to land properly. If gymnast makes it slowly he/she will not be able to complete these two twists and double backflips.

• Another thing to note: To generate the proper takeoff velocity and remain in the air long enough to complete the rotations, the gymnast must let go of the bar in a fully extended position. But in the extended position, one cannot make twists on air quickly. Thus during the twists the gymnast keep brings and keeps both hands closer to the chest, thus decreasing the momentum of inertia about the rotation axis (lies in a vertical plane), this increases the angular speed of twist using the Energy conservation. Thus he/she can complete the twists very fast.
• Then when the gymnast does the double backflip, he pulls the knees towards his/her chest, this way decreases the momentum of inertia about this backflip rotation axis (lies in the horizontal plane)., this way also gymnast can perform the backflip ferry quickly.
• After these two when the gymnast lands he/she spreads hand and leg to increase the momentum of inertia at maximum to decrease his/her rotation speed to very minimal, thus makes a safe gentle landing.