Term
| what is acceleration an effect of? |
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Definition
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Term
| What is another name for Newton's 1st law of motion, and what does it state? |
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Definition
| "The Law of Inertia" it states a body @rest, will stay @rest, and a body in motion, will stay in motion, unless a NET force acts on body |
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Term
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Definition
| a property of a body to resist a change (acceleration) in it's state of motion (change in it's velocity) |
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Term
| so in order to change an object's motion, what must be overcome? |
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Definition
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Term
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Definition
| quantity of matter (stuff) of which a body is composed, a direct measure of a body's resistance to change linear motion, it's inertia. |
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Term
| What is Newton's 2nd law? |
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Definition
"sum of the forces" and it is E(Sum)F = ma
unit: Newton |
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Term
| what direction is acceleration in when a gymnast is falling? |
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Definition
| in the same direction as the net force, in this case downwards |
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Term
| what are the characteristics of a force? |
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Definition
| it is a vector. so it has direction, magnitude, AND a point of application. |
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Term
| what are kinetics concerned with? |
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Definition
| they are concered with the CAUSES of motion |
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Term
| what is another name for Newton's 3rd law and what does it state? |
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Definition
"the law of action-reaction"
Every force has an equal and opposite force.
-where you find a force, you will find 2 interacting bodies (both contact and noncontact).
-Forces are always in pairs equal in magnitude, but opposite in direction |
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Term
| What are some implications of Newton's 3rd law? |
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Definition
you must draw (2) systems/objects.
"action-reaction": these forces happen simultaneously, NOT sequentially |
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Term
| what is kinetics concerned with? |
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Definition
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Term
| what does the gymnast and the footballer symbolize to us? |
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Definition
| that we must have knowledge of all three characteristics of a force to completely understand that a net force will have on an object's motion |
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Term
| what kinematic quantity allows us to measure the change in state of motion of an object? |
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Definition
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Term
| what type of acceleration is the body's mass? |
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Definition
| linear acceleration because "a" is in the equation for newton's second law, not alpha |
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Term
| newton's 3rd law deals with how many systems? |
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Definition
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Term
| newton's second law deals with how many systems? |
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Definition
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Term
| what are examples of contact forces? |
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Definition
| ground reaction force, joint reaction force, friction, elastic force, muscle force, etc. |
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Term
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Definition
| ground reaction force is the reaction force provided by the surface upon which one is moving. |
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Term
| what are characteristics of GRF? |
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Definition
| it is a vector so it can be resolved into its components. it changes in magnitude, direction, and point of application during the period an individual is in contact with the surface |
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Term
| Fx is also referred to as? for a GRF |
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Definition
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Term
| Fy is also know as? and is parallel or perpendicular to motion? |
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Definition
| anteriorposterior, and is parallel to motion because you look at running in a sagittal plane |
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Term
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Definition
| it acts at the center of mass of the total body |
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Term
| what is the formula for vertical motion? |
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Definition
(sum)F = m(body)*a(CoM)
so... (GRFv - W) = m(body)*a(CoM) |
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Term
If GRFv = W ... a = ?
If GRFv < W ... a = ?
If GRFv > W ... a = ? |
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Definition
If GRFv = W ... a = no net force, no acceleration in CoM
If GRFv < W ... a = (-)
If GRFv > W ... a = (+) |
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Term
| what type of force is friction and what does it oppose? |
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Definition
| it is a resistive force and it opposes RELATIVE motion |
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Term
| if you push on a chair and it doesn't move is there still friction? is friction force a constant? |
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Definition
| yes, external force is trying to move it. and no friction is not constant, there is a limiting value of friction. |
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Term
| how can we manipulate limiting value of friction? |
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Definition
| we can alter the max value of Flim by increasing Flim through football gloves, shoes, wax |
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Term
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Definition
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Term
| give an example when we want friction? when we don't want friction? |
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Definition
want: running, driving, walking
don't want: skiing, moving furniture |
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Term
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Definition
| F(friction) that is oppose the motion of the sliding object |
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Term
| what are the two states of sliding friction? |
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Definition
static: no sliding occurs, pushing force is EXACTLY matched by the friction force.
kinetic state: sliding occurs; pushing force exceeds F(lim) |
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Term
| what factors influence F(lim) |
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Definition
1. the force pressing the two surfaces together - normal reaction force (R)****
2. the nature of the two surfaces (u) |
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Term
| Rolling Friction or (RR) is produced when... |
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Definition
| one surface rolls over another. primarily it is due to a deformation of the surfaces in contact |
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Term
| is RR big or small? more or less than sliding friction? and what are three factors that influence RR? |
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Definition
| RR is small, usually less than sliding friction, and hardness of surface, force pushing surfaces together, and diameter of the rolling object |
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Term
| what is a definition of pressure and formula? |
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Definition
force applied over an area vs. a concentrated point, and P = force / area
unit: N/m^2 = pascal |
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Term
| force does not change between lying down vs. standing, rather ____ changes |
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Definition
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Term
| why is the concept of pressure important? |
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Definition
| important concept related to safety and injury protection, impact situations, the goal is to spread the force over as large an area of contact as possibel |
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Term
| how do crocs, a diabetic shoe, work? |
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Definition
| they take pressure away from the metatarsal heads |
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Term
| what is the difference in running barefoot versus with shoes? |
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Definition
| the pressure is extremely high barefoot |
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Term
| what were the results of caserotti et al.? |
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Definition
| jump height is higher in men, and higher power during concentric phase due to velocity component (not force) |
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Term
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Definition
| women and fiber type, the had a reduced max response execution speed, and lower recovery from falls |
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Term
| what is the stretch shorten cycle? |
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Definition
| an eccentric muscle contraction followed immediadetly by a concentric muscle contraction |
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Term
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Definition
greater range of motion, more cross-bridges, more coordinate, longer time period, elastic energy stored in tendon
JOINT MOMENTS ARE HIGHER in CMJ |
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