LECTURE #11 - work, power & energy Flashcards
what is “work, power, and energy” about ?
- continuation of linear kinetics
- causes of motion do not rely on solely newtons law of motion but also the relationships between work, energy, and power
what is work ?
product of force and amount of displacement in the direction of that force
what is displacement ?
the parallel displacement component relative to the force applied
what is the formula for work ?
W = F x d (force x displacement)
what is F = ?
average force computed over distance
what is the formula for work ?
J “joules”
what are the three things you need for calculating work ?
- average force acting on object
- direction of object acting on object
- displacement of object doing the line of action of the force during the time force act on it
what is a vector quantity ?
magnitude and direction
what are the two types of work ?
positive and negative work
what is positive work ?
if F and d parallel point in the same direction the work done is positive (going up)
what is negative work ?
if F and d parallel point in the opposite directions the work done is negative (going down)
how do you calculate displacement ?
final position - initial position
TRUE OR FALSE
“muscles perform work own bony segments, type of work depends on contraction type”
TRUE
what are the three types of muscle contractions ?
isometric, concentric, eccentric
define isometric :
zero work
define concentric :
positive work
define eccentric :
negative work
define energy :
the capacity
what are types of energy ?
mechanical, chemical, heat, sound, light, etc.
what is mechanical energy ? ;
energy of motion
what are the two forms of mechanical energy ?
kinetics energy and potential energy
what is kinetic energy ?
energy of motion (only posses kinetic energy while in motion)
what are 2 factors that influence KE ?
- mass of object
- velocity of object (large impact)
what is potential energy ?
energy of position (energy due to the change of position in gravitation field)
what is the formula for PE ?
mgh
what does PE = mgh stand for ?
m = mass
g = acceleration due to gravity (-9.81)
h = height of something above some reference line
FILL IN THE BLANK
“the work of a force is _______ to the cane in energy that it produces in the object acted on”
equal
FILL IN THE BLANK
“change in sum of forms of energy produced by a force is _______ to the mechanical work done by that force”
equal
what is the formula for W ?
W = TOTAL ENERGY
with an increase in work performed, does that mean increase or decrease energy change ?
increase energy change
what are two conditions requiring energy absorption ?
- catch a ball
- land from jump
(both of which are decreasing energy)
do muscles do positive or negative work on limbs ?
negative work
force needs to absorb KE depends on :
- how much KE is there to be absorbed
- distance over which force is applied
what is power ?
- rate @ which work is done
- rate @ which energy
FILL OUT THE BLANK
power can be _____ or _______
positive or negative
what is energy ?
the capacity to do work
what is power ?
rate of going work
what is potential energy ?
energy due to position
what is kinetic energy ?
energy due to motion
