Work, energy, power Flashcards
Equation for work
U = F•D
What happens to work in the example of benching up and then down?
Weight benched upward was positive work and going down is negative work. The total displacement is 0. Therefore no mechanical work!
What kind of work is exerted in the bench example?
Physiological work. Energy was expended to move the object, but no mechanical work!
What is positive work?
When force exerted displaces object in the same direction as force…. Throwing baseball
What is negative work?
When extorted force displaces object in opposite direction of force … Letting bench come back down
What kind of positive work can the body produce?
Concentric contraction to move the object in the direction of the force!
What kind of negative work can be done by the body?
Eccentric contraction. Force is produced by muscles but displacement in the opposite direction of the force exrted!
What kind of contraction produces no work?
Isometric contraction
What is energy?
The ability or capacity to do work… Heat, sound, deformation
What is kinetic energy?
Energy due to motion
What does kinetic energy depend on?
Mass and velocity
What is the formula for KE
1/2mv^2
Which is easier to determine, work or KE?
KE, b/c we can determine mass and velocity easier than force
What is potential energy?
Energy due to positioning
What are the 2 types of pot energy?
Gravitational and strain energy
What is gravitational energy?
Due to the position of an object relative to earth
What is gravitational PE related to?
Related to weight, elevation, height of the piece to some reference point
Equation for grav PE?
PE= mgh or WH
What is strain energy?
Due to the deformation of an object
What is the relationship of deformation to strain energy?
Linear relationship. As deformation increases, so does strain. Vice versa.
What is strain energy related to?
Objects stiffness, material properties, and deformation
What is the equation for SE?
SE = 1/2kx^2
K= spring constant X= amount of deformation
How is PE, KE, and SE related to a sports?
Energy possessed by the athletes due to motion, position and deformation
Law of conservation of energy?
Energy total n a system stays constancy, however energy in system can be changed from one form to another or transferred
What can work/energy principles prove?
Can explain the transferring of energy like catching a ball
How do muscles absorb energy?
Muscles have to do negative energy to absorb the energy. The force depended on the displacement, if too much force relative to displacement. Body will get injured for not absorbing all the energy
What can help absorb energy?
Pads (shock absorbing substances)
How can pass help landing?
Maximizes the displacement and minimizes force
What is power?
The rate of doing work
What is the equation for power?
P = U/t
U= FD
P=FD/T
V= D/T
Therefore, P = FV
What is the limitations of power produced by our muscles?
Contraction with high velocity will have less force. Vice versa. Inverse relationship.
What is the best choice of power?
Use the medium force and medium velocity to maximize power
At what percentage does power peak in max contraction velocity?
35-60%
What is work?
The product of force and the displacement in the direction of that force
