work power and enery Flashcards
can teh normal force ever do work on an object
yes acts on an object like jumping on elevator, the elvator on the psseneger object can be lifted up
why is it iring to push aginst a solid wall even though you are doing no work
convertin chemical energy to mechanical energy expending energy but not doing work
you lift a heavy book from a table to a high shelf list the froces on the book duringhte process describe whihc forces re doing work nd whihc froce you are doing work against
gravity and an applied force, they both do work, gravity bc pulling down and fa is pulling up positive so working agsint gravity that is pushing down
cana centripetal force ever do work on an object
no work done by a centripetal froce the velocity is tangential not parallel to the centripetal force the path is perpendicular not parallel
In what ways is the word work as used in everyday language the same as it is defined in physics in what ways is it different
Same because there is some effort like me bring a paper clip from a small stool to the tall table then putting it back down, different because there can be positive and negative work and energy is expended in some way like a rope pulling a box across the floor
What is negative and positive work
Negative has opposite direction and displacement and positive work is in the same direction like Vicky carrying the paper clips up and down
A woman swimming upstream is not moving with respect to the shore, is she doing any work if she stops swimming nad merely floats is work done on her
She’s not doing work on herself but on the water until she starts moving at a constant velocity and there is no kinetic energy there will be no work
Is work done by kinetic friction usually considered to be negative
Yes always negative because opposite direction of displacement
By approx how much does the gravitational potenatial energy change when you jump as high as u can
Dependent on the height
Explain how a simple pendulum illustrates the law of conservation of energy
It needs to have energy to start with and with work there u get energy because the work works against gravity give potential energy there has mgy then when released the potential energy starts to convert to kinetic energy and heat until kinetic energy is at the max at the bottom then the reverse process happens going up again if there is air resistance there is loss of heat if there isn’t air resistance there is no loss of heat and the pendulum will go forever
Suppose you lift a suitcase from the floor to the table the work you do on the suitcase depends on which of the following: whether you lift it straight up or a more complicated path, the time it takes, the height of the table, and the weight of the suitcase— do the same with power rather than work
Depends on the height of the table and the weight of the suitcase because of the formula work equals the force times the distance times the angle where the force is the weight of the suitcase and the distance is teh height you lift it — power depends on the time it takes, the height of the table and the weight of the suitcase because of the formula where power equals the work which is the weight of the suitcase divided by the time it takes
Why does a grandfather clock must be wound up periodically
There is friction and air resistance if there was no friction or air resistance there would be no loss of heat so it would continue on infinitely but there is loss of heat so every time it slows down more until you have to wound it up again
