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58 Cards in this Set
- Front
- Back
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energy
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ability to do work
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when we put a force on an object and a displacement occurs
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define work
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work
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only occurs when the force and displacement share a common direction
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position or motion
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in order for work to be done, a force must change blank or blank
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frictionless surface at constant velocity
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when is work not done
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w=Fd
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work formula
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J
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unit for work
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motion
energy |
force changes blank
work changes blank |
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any energy associated with position or state of motion of an object
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define mechanical energy
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energy
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can't have blank without mass
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energy that an object has due to its state of motion
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define kinetic energy
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ke=1/2mv^2
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kinetic energy formula
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j
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units for kE
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scalar
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KE is a blank quantity
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scalar
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work is a blank quantity
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if the work done on a n object only changes its speed, then work changes object's KE
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work kinetic energy theorem
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work kinetic energy theorem
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if the work done on a n object only changes its speed, then work changes object's KE
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W=KEf-KEi
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formula for work kinetic energy theorem
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Fd=1/2mv^2-1/2mv^2
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alternate formula for work kinetic energy theorem
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application of force and movement of something by force
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in order for work to be done, must have a) b)
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no movement, no force, force and distance perpendicular
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no work done if (3)
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holding bowling ball overhead
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ex of no work done because of no movement
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hockey puck coasting at a constant speed on frictionless ice
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ex of no work because no force
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carrying a book bag or any object
earth orbiting sun |
ex of no work because force and distance are perpendicular
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energy an object has due to its elevated position above earth's surface
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define gravitational potential energy
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GPE=mgh
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formula for gravitational potential energy
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scalar
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gpe is a blank quantity
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F=-kx
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hooke's law
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N/m
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units for spring constant
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energy associated with a compressed or stretched spring
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define elastic potential energy
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EPE=1/2kx^2
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formula for elastic potential energy
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the total amount of ME in a system remains constant, provided only conservative forces are acting on system
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define conservation of mechanical energy
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MEi=MEf
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formula for conservation of mechanical energy
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keep mechanical energy as mechanical energy gravitational, spring
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conservative forces
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transform mechanical energy into other types friction, air resistance
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nonconservative forces
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change in energy per unit of time
work done per unit of time how fast energy is transferring |
define power (3 ways)
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J/s or Watts
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units for power
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P=Fd/t
P=W/t P=Fv |
formulas for power (3)
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a device that increases the distance over which work is done in order to decrease the force applied to do the work
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define simple machine
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measure of the quantity of motion an object has
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define momentum
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p=mv
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formula for momentum
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kgm/s
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units for momentum
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vector
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momentum is a blank quantity
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momentum
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a fast moving bullet and a slow moving car can have same blank
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change in momentum
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impulse
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fdeltat or deltap
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formula for impulse
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fdeltat=mdeltav
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impulse momentum theorem formula
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motion
momentum energy |
force is applied to cahnge blank
impulse is applied to change blank work is applied to change blank |
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decreasing momentum over a long period of time
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egg in sheet
car hitting wall vs haystack padded dashboard airbags catching baseball with glove jumping off table knee pads, shin guards boxer |
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increase time, decrease force.
small force, larger time |
explain egg in a sheet
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increasing the time of impact, decreasing force of impact. utilize decreasing momentum over time. goal is to minimize force
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physics of cushioning
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follow through
increase force and time hit object as hard and as long as possible |
how do you maximize a change in momentum?
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object must be stopped and thrown back
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why is the impulse much higher when an object bounces
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the total linear momentum of a system does not change if there are no net external forces
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define law of conservation of momentum
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Pi=Pf
m1v1+m2v2=m1v1+m2v2 |
formula for law of conservation of momentum
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collision in which objects bounce apart
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elastic collision
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objects remains stuck together
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inelastic collision
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elastic
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in perfectly blank collisions, no kinetic energy is lost
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