Work, Power and Energy Flashcards
(19 cards)
Define work
Performed when an object is displaced by the application of a force (W=Fd)
In what situation is work positive
When the force and the distance are in the same direction
In what situation is work negative
When the force and distance are in opposite directions
What is energy?
The capacity (ability) to perform work
T/F work is a transfer of energy
True (w= deltaE)
Give 4 examples of positive work
A pitcher throwing a ball, a weightlifter does positive work when lifting a weight, a gymnast pulling up on the uneven bars, a high jumper jumping off the ground
Give 4 examples of negative work
a first baseman catching a ball, a weightlifter lowering a weight, a gymnast landing from a dismount.
Friction also does negative work on a skier sliding down a hill
What is mechanical work?
Wf-Wi
Define power
Used to express the amount of mechanical work performed in a given time interval
What is power in relation to energy
Because work is a transfer of energy, power is the time rate of energy transfer
How does time affect power
If the same amount of work is done in a shorter time, power will be greater
What is mechanical energy composed of?
Energy associated with motion, position or deformation
Define kinetic energy
The energy associated with motion
Define gravitational potential energy
Potential energy that an object has because of its position relative to a reference surface
Define electrical potential energy
Potential energy stored in a deformed object (e.g. a spring)
What is the law of conservation of mechanical energy?
In the absence of externally applied forces other than gravity, the total mechanical energy of a system remains constant
What effect does gravity have on mechanical energy?
I will not have an effect on Etotal, but will cause the switch between kinetic energy and potential energy
What is the conservation of mechanical energy attributed to?
One form of energy being transferred into another
Describe the work-energy relationship when there are no external forces that act on the system other than gravity
In this situation, no work can be done because no external forces act. If no work can eb done, the total mechanical energy of the object is conserved. The total mechanical energy of the object is constant if no external forces other than gravity act on it
