Lectures 2-3 Flashcards
(37 cards)
What is human motion caused by?
Levers being accelerated about axes. This occurs through torque.
What is torque?
Muscle contraction.
What are the 4 types of motion?
- No displacement
- Linear Displacement
- Rotational Displacement
- Displacement-to-Stationary
Describe “no displacement” in terms of centre of mass.
The centre of mass must be over or directly in between the base of support.
What is the centre of mass? (3)
- The point in which the bodies mass is equally distributed in all directions.
- The balance point of the body.
- Point in which the body rotates free in space.
Define balance.
Process whereby the body’s state if equilibrium is controlled for a given purpose.
Define equilibrium.
The state of a system that is not experiencing any change in its direction or speed.
Define stability.
How easily one can disrupt their equilibrium.
What are 4 ways one can increase their stability?
- Increase the size of the base of support
- Increase the inertia of the body
- Decrease the distance between the centre of mass and the base
- Keep the line of gravity closer to the middle of the base
What are 3 axes of rotation?
- Longitudinal axes
- Transverse axes
- Anterior/Posterior axis
What is the longitudinal axis?
Works top to bottom and is most common (walking, spinning, etc.)
What is the transverse axis?
Works side to side (sitting up, rolling, flipping, etc.)
What is the Anterior/posterior axis?
Works front to back and is the least common (cartwheels etc.)
When is linear displacement caused?
If a forces pass directly through centre of mass, they will cause linear motion.
What is rotational or angular displacement?
When the body moves along a circular path, through the same angle, in the same direction, and at the same time.
What is the axis of rotation?
A fixed pivot point.
How is rotational motion produced?
When forces pass off centre. The further off centre the force is the greater the rotation.
What are two factors that influence rotational motion?
Force and the distance force is applied away from axis of rotation.
How does one calculate torque (movement of force)?
The moment arm multiplied by the force.
What is the “moment arm”?
The distance from the force to the axis of rotation.
What is a first class lever?
Pivot point placed between the load and the effort, as in the seesaw, crowbar, and balance scale.
What is a second class lever?
The load is between the effort and the fulcrum. A wheelbarrow is a second-class lever..
What is a third class lever?
The effort is placed between the load and the fulcrum. The effort always travels a shorter distance and must be greater than the load. A hammer acts as a third-class lever when it is used to drive in a nail.
What are two types of motion-to-stationary motion?
- When energy is attenuated over time
2. When energy is attenuated over surface area.
