Physics of Torque and Angular Momentum

Biomechanical Principles

• Seven biomechanical principles are outlined by the Coaching Association of Canada's National Coaching Certification Program (NCCP)
• These principles help kinesiologists and other movement professionals give effective feedback to students, athletes, or clients, to improve their movement patterns
• Understanding static and dynamic systems and their roles in human movement is enhanced by learning biomechanical principles.

Static Systems

• Statics is the branch of mechanics dealing with objects or bodies in a state of constant, unchanging motion.
• In static systems, the rate of change of motion for any object is unchanging over time. (Examples include a gymnast holding a stationary pose or a high diver in free fall)
• If an external force is applied to a body and causes its rate of motion to change, the system becomes dynamic

Dynamic Systems

• Dynamics is the branch of mechanics studying changes in the motion of objects or bodies caused by forces.
• A dynamic system experiences a change in its rate of movement due to applied forces. (Example: A rugby player changing direction in a match)
• Changes in movement patterns are a result of internal and external forces acting upon the body.
• Biomechanical principles involve the interaction between static and dynamic systems.

The Seven Principles (Short Form)

• 1: Stability: Greater mass, lower center of mass, larger base of support, and a center of mass closer to the base of support leads to increased stability.
• 2: Production of Maximum Force: Uses all possible joint movements contributing to the task objective. High-intensity, slow, controlled, and simultaneous movements are best.
• 3: Production of Maximum Velocity: The larger, slower joints initiate movement. Smaller, faster joints are involved later.
• 4: Impulse-Momentum Relationship: The greater the impulse applied, the greater the increase in velocity. Impulse occurs when a force is applied over a period of time.
• 5: Direction of Application of the Applied Force: Movement occurs in the opposite direction of the applied force. Newton's third law of motion applies.
• 6: Production of Angular Motion (Torque): Angular motion is produced by applying a force at a distance from an axis (torque).
• 7: Conservation of Angular Momentum: Angular momentum is constant when an object or individual is free in the air.

Key Concepts

• Mass: The quantity of matter contained within an object or body.
• Centre of mass: The imaginary middle point around which an object's mass is balanced.
• Base of support: The supporting area beneath an object or body defined by points of contact with the supporting surface.
• Stability: The quality of being stable and resisting change in motion.
• Balance: An even distribution of mass allowing something to remain steady.

Exit Question (Page 13)

• What factors affect how stable an individual is while performing a physical task?

Principles of Maximum Effort (Page 14)

• In many activities, maximum effort is needed to complete a specific task.
• Two biomechanical principles relate to maximum effort: producing maximum force, producing maximum velocity.
• The focus question: How can maximum effort be produced during a physical task?

Principle 2: Production of Maximum Force (Page 15)

• The production of maximum force requires the use of all possible joint movements that contribute to the task's objective.
• This principle is often observed in lifting or performing other tasks requiring strength, and involves slow, controlled, and simultaneous high-intensity movements and sequenced joint rotations.
• If any joints experience restricted range of motion (ROM), fewer muscles will likely be able to contribute to the movement.

Principle 2 in Action (Pages 16-17)

• Running, a young baseball player swinging a bat, and a baseball player hitting a pitch are examples of this principle.
• These involve joint rotations at the ankles, knees, and hips; sequenced contractions of multiple muscles; and the use of all possible joints in a sequential way to maximize force.

Principle 3: Production of Maximum Velocity (Page 18)

• Maximum velocity production requires the use of joints starting from the largest and slowest ones to smaller and faster joints.
• For example, in a tennis serve, golf swing, or baseball pitch; the larger, slower joints (like the hips) initially initiate the movement, followed by the smaller, faster joints (like the wrists and fingers).

Example of Principle 3 in Action (Pages 19-22)

• Baseball throwing, fly fishing, and golfing are examples. These activities require a sequence of joint actions to produce maximum velocity—e.g., leg movements followed by hip rotations and then arm/wrist rotations.

Exit Question (Page 23)

• How can physical movements that involve linear motion (translational) be optimized??

Biomechanical Principles 4 & 5: Linear Motion (Page 24)

• Two principles relating to linear motion are: Impulse-Momentum Relationship, and Direction of Application of the Applied Force.

Principle 4: Impulse-Momentum Relationship (Page 25)

• The greater the impulse applied, the greater the increase in velocity of the object (e.g cricket ball)
• Impulse is a force applied over a time period to an object.

Imparting High Velocity to a Cricket Ball (Page 26)

• Applying a significant impulse allows the hitter to impart a high velocity to the ball.

Principle 4 in Action (Pages 27-28)

• High jumping, volleyball serve are examples.

Principle 5: Direction of Application of the Force (Pages 30-33)

• Movement usually occurs in the opposite direction to the applied force.
• This is evident in a variety of sports like swimming, football, and hockey.

Exit Question (Page 34)

• How can we optimize physical movements that involve linear (or translational) motion?

Biomechanical Principles 6 & 7: Angular Motion (Page 35)

• Two principles relating to angular motion (rotational motion) are Production of Angular Motion (torque), and Conservation of Angular Momentum.

Principle 6: Production of Angular Motion (Torque) (Page 36)

• Angular motion is generated by a force applied at a distance from an axis (torque).
• The factors that affect the amount of torque are the applied force, length of the lever arm, and the angle of application.

Factors Affecting Torque (Page 37)

• The amount of torque produced depends on applied force, length of the lever arm and the angle of the force's application.

Example of Principle 6 in Action (Page 38)

• Application of torque is evident in tasks such as loosening a bolt.

Generation of Torque at Human Joints (Page 39)

• An illustration of torque generation at a knee joint.

Principle 7: Conservation of Angular Momentum (Page 40)

• Angular momentum is constant for a freely moving object in the air.

Principle 7 in Action (Page 41)

• Various activities such as trampoline, gymnastics, aerial skiing and diving require angular momentum conservation.

Adjusting the Moment of Inertia (Page 42)

• Adjusting the moment of inertia is important for many activities such as a sports where rotation is involved.

Principle 7 in Action (Page 43)

• Activities like high diving, figure skating.

The Law of Conservation of Angular Momentum (Page 44)

• Rotational movement is governed by the principle that the total angular momentum of a body will remain constant unless a torque acts on it (i.e. resistance is encountered).

The Law of Conservation of Angular Momentum (Page 45)

• In spinning events, bodies (e.g., a figure skater) can change their angular velocity by adjusting their moment of inertia (for example, by pulling in their limbs when turning rapidly).

Exit Question (Page 46)

• How can we optimize physical movements that involve angular (or rotational) motion?

Homework (Page 47)

• Complete pages 190-199 of the workbook.

This quiz explores the concepts of torque and angular momentum, focusing on factors that influence torque generation and the law of conservation of angular momentum. Answer questions about the relationships between moment of inertia, angular velocity, and techniques to optimize athletic movements. Test your understanding of physics principles applied to real-world scenarios.