ENERGY WORK POWER Flashcards
energy
the ability to do work
energy is a scalar or vector
scalar
translational kinetic energy
capacity to do work by virtue of a body’s linear motion
rotational kinetic energy
capacity to do work by virtue of a body’s rotational motion
gravitational potential energy
capacity to do work by virtue of a body’s position
describe gravity in gravitational potential energy formula
gravity will be input as positive because you can’t have negative energy
can you have negative energy
NO
strain/spring potential energy
capacity to do work by virtue of a deformed body returning to its original shape
what is k in the strain/spring potential energy formula
spring constant
-the stiffness of the spring
describe example of strain/spring potential energy
an eccentric movement like a golf swing that stretches the tissues (stores potential energy in the tissue itself)
-benefit from the concentric of the movement
heat energy
energy lost is dissipated as heat
-micro-movement of particles
work
change in mechanical energy
mechanical energy
kinetic + potential energy
if movement is in the opposite direction as the force applied then work will be positive/negative
-what type of movement
-what occurs
-name an example of this for a push up
negative
-eccentric movement
-attempting to decelerate the body absorbing kinetic energy
-down phase of push up
if movement is in the same direction as the force applied then work will be positive/negative
-what type of movement
-what occurs
-name an example of this for a push up
positive
-concentric movement
-attempting to accelerate the body generating kinetic energy
-up phase of push up
if no movement occurs, with applied force, describe mechanical work
-what type of movement
-name an example of this in exercise
mechanical work = 0
-isometric movement
-isometric plank
ergometry
quantifying work performed by the body
-change in energy
conservative force
a force where work done by that force in moving an object from starting point A to end point B is independent of the path the object takes
example of a conservative force
gravity
-work done by gravity is not path dependent
name a non-conservative force
friction
does conservative force mean positive work
NO
-just because a force has done negative work doesn’t mean that the force was not a conservative force
-spring forces + gravitational forces store potential energy as they perform negative work on an object
conservation of mechanical energy
when all forces acting on a body are conservative the body’s total mechanical energy remains constant (projectile motion)
can COM be outside physical body
yes
Fosbury flop
passing body over bar causes COM to pass under bar
ergometer
work-measuring device
-measures torque over a certain displacement
point mass method
work as a change in total energy of the COM
-estimate a body as behaving as just a single COM + quantify changes in energy by changes in the gravitational + translational kinetic energy of the body
what doesn’t the point mass method account for
rotational kinetic energy
what is point mass method termed
zero work paradox
zero work paradox (for point mass method)
even though you may be putting a lot of effort into a movement, depending on what that movement is, it may not show up in the point mass method
-EX: walking
-1 cycle of walking- heel strike on right side through gait cycle back to heel strike on right side
-point pass method would estimate 0 work done; limited for calculating work of a body when you get back to the same point
what does mechanical efficiency in biomechanics take into account
physiological cost
-uses gas exchange to figure out metabolic cost for things like a walk
power
the rate at which work is performed
-rate of energy generation or dissipation
what is the integral of power (area underneath the power curve)
work
work is the are under what curve
joint power curve
above 0 on joint power curve = ?
positive work
-concentric muscle conctraction
below 0 on joint power curve = ?
negative work
-eccentric muscle contraction
