Work
SI unit for mechanical work
Joule (J)
Capacity to do work based on vertical position
Potential energy
As the duration of a physical task increases what happens to the ability to produce high average power output?
Decreases
The fastest pitch ever recorded is 105.8 mph (47.3 m/s). What work was required to achieve this pitch velocity? The mass of an average baseball is 0.15kg.
167.8 J
Best mechanical indicator of the intensity of a physical task
Power
How much work is performed during the eccentric phase of a military press of a 650 N barbell that was displaced 0.5m vertically?
-325 J
What is the KE possessed by an elite 86.6kg athlete sprinting at 8.9 m/s?
3430 J
SI unit for Power
Watt (W)
What is the force applied during the catch of a softball (m = 0.18kg) travelling at 34.9 m/s if the glove shift 0.1m backwards during the catch?
1096 N
During the lifting portion of a back squat, what are the muscles involved, type of muscle action, and joint motion of the knee?
knee extensors (quads), concentric, extension
Positive work is performed on an object in motion, what will happen to the mechanical energy of the object?
Increase
A high jumper leaves the ground with 900 J of mechanical energy. At the apex of the trajectory, what is the vertical kinetic energy?
0 J
Which of these influence the ability of humans to produce and sustain power?
Muscle length, task duration, muscle shortening velocity, mass, metabolic system
All of these
Which of these are vector quantities: work, kinetic energy, potential energy, power
Trick question: None
How much total work is performed on the bar during performance of a bench press with a 1000 N barbell?
0 J
What is the impact velocity of a 58.3 kg person falling from a height of 3.48m?
8.26 m/s
A 64 kg athlete runs up a hill in 8 s. If the hill is 15 m high, what was the average power produced during the run?
1177.2 W
An individual performs two drop landings from the same height above different basketball floors. The first landing is on a traditional hardwood floor; the second is on a suspended hardwood floor. Will there be a difference in the mechanical work performed on the individual, why? Will there be a difference in the net vertical force, why?
Work is the same during both landings because the change in mechanical energy is the same. The net force will be less for the second landing because the displacement in the vertical direction is greater.
A t-shirt cannon launches a shirt with a resultant velocity of 8 m/s at an angle of 23 degrees. The shirt weighs 0.15kg. How high will the t-shirt travel?
0.5m
What is the primary factor that limits humans' ability to sustain power?
The metabolic system