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Biomechanics Test 3
| Question | Answer |
|---|---|
| Newton's 1st Law of motion: Inertia | A body will maintain a state of rest or constant velocity unless acted on by an external force that changes the state. |
| Newton's 2nd Law of motion: Acceleration | A force applied to a body causes an acceleration of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body's mass. |
| Newton's 3rd Lawof motion: Reaction | For every action, there is an equal and opposite reaction. |
| What does force cause? | deformation and or motion |
| what is force? | push or pull, and a vector quantity |
| internal forces | act within the object or system. Hold together when acted on by external forces |
| external forces | Act on an object as a result of interaction with environment. Contact forces: forces resulting from objects coming into contact |
| exmaples of internal forces | muscle tension, ligament tension, bone compression |
| examples of external forces | Gravity, magnetic, electrical |
| normal force | force actin perpendicular to surface of object (NET FORCE) |
| Tangential force | force acting parallel to the surface object (FRICTION) |
| What is Net force | Single resultant force derived from the vector compositon |
| what is Friction | Forc acting over the area of contact between two sufaces in the direction oposite that of motion or motion tendency |
| Maximum static friction | Maximum amount of friction that can be generated between two static surfaces. |
| Kinetic friction | Constant-magnitude friction generated between two surfaces in contact. |
| Coefficient of friction | Number as an index of the interaction between two surfaces in contact. |
| Torque | The rotary effect of a force about an axis of rotation, measured as the product of the force and the perpendicular distance between the forces line of action and the axis. |
| Moment arm | Shortest (perpendicular) distance between a forces line of action and, an axis of rotation. |
| What I the formula for torque ? | T=Fd |
| Lever | A simple machine consisting of a relative rigid, bar like body that may be made to rotate about an axis. |
| Fulcrum | The point of support, or axis, about which lever may be made to rotate. |
| 1st class lever | Lever positioned with the applied force and the resistance on opposite sides of the axis of rotation. |
| 2nd class lever | Lever positioned with the resistance between the applied force and the fulcrum. |
| 3rd class lever | Lever position with the applied force between the fulcrum and the resistance. |
| Mechanical advantage | Ratio of force arm to resistance arm for a given lever. |
| Static equilibrium | A motionless state in which there is no net force or net torque acting. |
| Center of gravity | The point about which a body's weight is equally balanced in all directions. or center of mass or mass centroid. |
| Stability | Resistance to disruption of equilibrium |
| Balance | A persons ability to control equilibrium |
| Base of support | Area bound by the outermost regions of contact between a body and support surface or surfaces. |
| Contact Forces | Fluid Resistance, Inertial force, Muscle force, Elastic force, ground reaction force, joint reaction force, Friction. |
| Non-Contact Forces | Gravity, magnetic, eletrical |
| Momentum? | quantity of motion possessed by a body. measured as the product of a body's mass and its velocity M=mv |
| Principle of Conservation of MOmentum? | in the absence of external forces, the total momentum of a given system remains constant. |
| What causes Momentum? | Impulse: the product of a force and the time interval over which the force acts |
| impact | a collision characterized by: the exchange of a large force, during a small time interval. |
| the nature of the impact? | the coefficient of restitution, a number that serves as an index of elasticity for colliding bodies; represented as e. |
| what does the coefficient of restitution describe? | -e= relative velocity after impact/relative velocit before impact. |
| what is mechanical work? | the product of a force applied against a resistance and the displacement of theresistance in the direction of the force. |
| mechanical power? | the rate of work productuon. calculated as work divided by the time over withich the work was done. |
| mechanical energy ? | the capacity to do work, the units are Joules (3 forms of energy potiental, kinetic, thermal). |
| law of conservation of mechanical energy? | when gravity is the only acting external force, a body's mechanical energy remains constant. |
| the princile of work and energy ? | the work of a force is equal to the change in energy that it produces in the object acted upon. |
| angular inertia | the property of an object to resist changes in its angular motion. |
| angular inertia formula | I=mr2 (i=moment of inertia, m=mass of segment, r=radius of mass from axis of rotation) |
| Radius of Gyration (K) | masses are not cencentrated into single points. Mass is spread out along the radius and has shape. |
| angular momentum | has size and direction, direction is same as the angular velocity that defines it |
| conservation of angular momentum | based on Newton's first law. declares that the angular momentum of an isolated system will remain the same regardless of any movements or torques that are produced internal to the system. as long as no external force is applied. |
| angular acceleration | directly proportional to magnitude of external torque. invcersely proportional to the moment of inertia with respect to axis of rotation. |
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