Why does a springboard diver bring her knees and arms closer to her body during a somersault?

What effect does bringing her knees and arms closer have on the diver?

Why does the diver bring her knees and arms closer during the dive?

Effect of Bringing Knees and Arms Closer

When a springboard diver brings her knees and arms closer to her body during a somersault, it has a specific effect on her motion in the water. This action decreases her moment of inertia and increases her angular velocity.

The law of conservation of angular momentum states that if no external torque acts on a body, the angular momentum remains constant. The formula for angular momentum is L=Iω, where I is the moment of inertia of the diver and ω is her angular velocity. As the diver rotates her body about an axis perpendicular to the plane of her body, the moment of inertia plays a crucial role in determining her rotation speed.

Considering the diver as a collection of particles of different masses (m1, m2, ..., mn) situated at varying distances (r1, r2, ..., rn) from the axis of rotation, the moment of inertia can be calculated using the formula I=Σmr^2. When the diver jumps and initiates the dive at an angle, she possesses a specific initial angular momentum.

During the dive, as no external torque acts on her, the principle of conservation of angular momentum dictates that her angular momentum must remain constant. Therefore, the equation Iω=constant holds true throughout her motion. By bringing her arms and knees closer together, the diver effectively reduces her moment of inertia, as the distances of her arms and knees from the axis of rotation decrease.

Since ω is inversely proportional to 1/I (angular velocity is proportional to the inverse of moment of inertia), the reduction in moment of inertia leads to an increase in angular velocity. Consequently, the diver is able to spin faster and complete the somersault more efficiently when her knees and arms are brought closer during the dive.