Chapter 3: Part 3

Question 1

What is angular momentum and what is the rule when it is airborne?

Answer 1

The amount of angular motion possessed by a body.

When airborne, angular momentum is conserved and always remains the same

Question 2

What is the equation for angular momentum?

Answer 2

Angular Momentum = Moment of Inertia x Angular Velocity

Question 3

What is moment of inertia defined as, and provide an equation?

Answer 3

The tendency of an object to resist changes to its rotary motion
Mass x Radius Squared

Question 4

In which sports do athletes constantly change their body configuration?

Answer 4

Ice skating, diving, gymnastics

Question 5

How can athlete manipulate moment of inertia to improve performance?

Answer 5

By increasing the radius of rotation from the axis of rotation, the moment of inertia increases which slows down the speed of rotation

Question 6

How is angular momentum manipulated in gymnastics to improve performance?

Answer 6

When rotating in the air, the radius can be decreased by tucking, which decreases moment of inertia. As angular momentum is conserved, there is a proportional increase in angular velocity, thus a gymnast can somersault faster and complete more rotations, before extending their legs to reduce angular velocity to prevent over rotation when landing

Question 7

What does a decrease in the radius of rotation result in and provide an example?

Answer 7

Decreased moment of inertia, increased angular velocity

Tuck in gymnastics

Question 8

What does an increase in the radius of rotation result in and provide an example?

Answer 8

Increased moment of inertia, decreased angular velocity

Pike in gymnastics

Question 9

How does angular momentum affect the performance of a junior player using a longer and heavier bat?

Answer 9

By increasing both the mass and radius squared with a longer and heavier bat, the moment of inertia is increased and the angular velocity is decreased, resulting in the junior player not being able to generate enough angular motion, swinging the bat slower and hitting the ball a shorter distance

Question 10

What is Newton’s first law of angular motion defined as?

Answer 10

Angular momentum of a body remains constant unless acted upon by an external torque

Question 11

What is a sporting example of Newton’s first law of angular motion?

Answer 11

An ice skater will continue to rotate in the same direction at the same angular velocity, unless an external torque such as friction is applied

Question 12

What is Newton’s second law of angular motion defined as?

Answer 12

A torque applied to an object will cause a change in angular motion in the direction of the applied torque, that is directly proportional to the size of the torque applied, and inversely proportional to the moment of inertia on the object

Question 13

What is a sporting example of Newton’s second law of angular motion?

Answer 13

The greater the torque applied to the pedal on a bike, the faster the wheel will rotate, and the faster the cyclist will travel

Question 14

What is Newton’s third law of angular motion defined as?

Answer 14

For every torque, there is an equal and opposite torque

Question 15

What is a sporting example of Newton’s third law of angular motion?

Answer 15

When a volleyball player swings their arm back in a clockwise direction to spike, their legs move ion an anticlockwise direction to oppose the torque upon their body

Question 16

What is summation of momentum defined as?

Answer 16

The combination of forces produced by different body parts, each building upon the momentum of the previous body part

Question 17

How can athletes summate their momentum to generate the greater velocity?

Answer 17

Athletes start a movement with larger, heavier muscles to generate greater force and stability. Since momentum is conserved, when this force is transferred to body parts of less mass, they generate much greater velocity and improve performance

Question 18

How can an athlete launch a projectile with optimal velocity?

Answer 18

• Use as many body parts as possible
• Use the correct sequence of heavier and slower body parts to lighter and faster body parts
• Use the correct timing by moving the next body part once the previous body part has reached optional velocity
• Ensure each body part is stabilised before momentum is transferred
• Follow through is important to ensure that the last body part does not slow down