Term
Work & Energy are vector/scalar quantities 

Definition


Term

Definition
work is done on an object by a constant force.
This force is constant in both magnitutiude & direction. 


Term
Work defintion in terms of energy 

Definition
work is change in mechanical energy 


Term

Definition


Term
If motion and force are in the same direction so that :
θ = 0
cos θ = 0
what will work be? 

Definition
W= Fd
For ex you push a cart 50 m with 30 N of force your work will be
W= 30 x 50
=1500 J 


Term
T or F: Can force can be exerted on an object & do no work? 

Definition
True,
ex you carry a grocery bag at rest
OR
if you carry it horizontally across the room at a constant velocity
(this b/c there is horzontial force required to MOVE the bag at a constant velocity)
therefore theta is 90 and cos 90 =0
b/c displacment is perpendicular to force 


Term
Energy is a (conserved/nonconserved) quantity


Definition
conserved, energy is not lossed or gained 


Term

Definition


Term
If gravity & normal force are perpendicular (90 angle) _____ work is done 

Definition


Term
translational kinetic energy is defined by what quanity? 

Definition
KE= 1/2mv^{2}
aka work is force x displacment 


Term
The work energy principle defined 

Definition
the net work done on object is equal to the change in the object's kinetic energy. 


Term
Give the formula for work energy principle 

Definition
W_{net= ΔKE}
OR
W_{net= KE}_{2  KE}_{1} 


Term
Work done by forces that ____ the direction of motion such as _____ will be negative 

Definition


Term
Do centripetal forces do work? 

Definition
No, they are always perpendicular to motion 


Term

Definition


Term
if mass is doubled then kinetic energy is 

Definition


Term
if velocity is doubled then kinetic energy 

Definition
4x times greater
=
is capable of doing 4x more work 


Term
If the net work (W) is positive then KE ___
If the net work (W) is negative then KE ___
If the net work is (W) is zero then KE 

Definition
1. Increases
2. Decreases
3.same 


Term
Potenital Energy is defined as 

Definition
energy associated with forces that depend on the position or configuration of an object/s
REALTIVE to
surroundings



Term
examples of potential energy include 

Definition
woundup spring(waiting to be released)
stretched elastic band (waiting to be released)
an object at some height above the ground
(like a cup on a counter) 


Term
give formula that combines friction and Work by a nonconservative force 

Definition
F_{fr}d = 1/2mv_{22}  1/2mv_{1}^{2} mgy2mgy1
friction= (KE2KE1)(PE2PE1) 


Term
Recall the previous example:
object at some height above the ground
(like a cup on a counter)
is an example of what specific potential energy? 

Definition
potential gravitational energy
(b/c of its position realtive to Earth) 


Term
Potential Energy: In raising a mass 'm' to a height 'h', the work done by the external force is expressed by what equation: 

Definition
W_{ext}= F_{ext} d cos 0
= mgh
W_{ext}=mg (y2y1)
W_{ext = }PE_{2}PE_{1}
=ΔPE



Term
Official formula for gravitational potential energy 

Definition
PE_{grav}= mgy
m= object mass in kg
g= 9.8 m/s
y= height in m 


Term
Gravitational Potential Energy can become ______ if the object is dropped. 

Definition


Term
Potential energy is property part of 

Definition
system NOT whole b/c it depends on external forces 


Term
Gravitational Potential Energy: The change in potential energy in terms of the work done gravity itself can be written as: 

Definition
W_{G}= mg (y_{2} y_{1})
W_{G=  }(PE_{2 } PE_{1})
W_{G=  Δ PE}
therefore the work done by gravity on an object is NEGATIVE 


Term
Gravitational P.E. depends on 

Definition
the VERTICAL height of the object above some reference level. 


Term
The force to compress or stretch a spring is represented by what formula? 

Definition
F_{s} =  kx
where
k= spring constant
x= distance 


Term
the further the spring is compressed or stretched causes the force is _____ 

Definition


Term
Give the formula to find the potential energy in a stretched/compressed string measured from its equilibrium positon


Definition
elastic PE= 1/2 kx^{2}
scalar value
where x is the amount of spring stretched/compressed (meters)
units: N 


Term
Is there a single formula for potential energy? 

Definition
no, it depends on the force involved.
note: kinetic energy does,
1/2mv^{2} 


Term
Nonconservative force def 

Definition
work that is done by a force that depends on :
path
start point
end point
ex: friction 


Term
conservative force defined 

Definition
work depends on intial + end position NOT PATH
ex. gravity 


Term

Definition


Term

Definition


Term

Definition


Term
friction is a _____ force 

Definition


Term
tension in a cord is a ____ force 

Definition


Term
push or pull by a person is a ____force 

Definition


Term
Work done by a nonconservative force is equal to 

Definition
the total change in kinetic & potential energies 


Term
Give the formula for work by a nonconservative force 

Definition
W_{NC} = ΔKE +ΔPE
1/2mv_{12}^{ }+ mgy_{1 =} 1/2mv_{2}^{2 }+mgy_{2}
* remember friction, tension are ex 


Term

Definition
when there are NO nonconservative forces
* the kinetic & potential energy changes are equal but opposite in sign
(5 and + 5) 


Term
Define the principle of total mechanical energy 

Definition
if onlt conservative forces are acting, the total mechanical energy of a system neither decreases or increases in ANY process .
(aka it is conserved). 


Term
Give the formula for the total mechanical energy 

Definition
E= KE + PE
E= 1/2 mv^{2} + mgy
recall this is energy is constant
E1 =E2
energy before=
energy after 


Term
The rollercoaster problem:
If there is no friction, then the speed of the rollercoaster will depend on 

Definition
current height compared to its starting height 


Term
if there is a nonconservative force like friction, where does the KE +PE go?


Definition
become heat & temp of materials can be calculated 


Term

Definition
rate at which work is done 


Term
unit for power (P)
capital P 

Definition


Term
P (average power) = (in words) 

Definition
work/time
=
energy transformed 


Term
P (average power) =
in terms of force & average velocity 

Definition


Term
P = W /t
give another formula for average power in terms of potential energy 

Definition


Term
air resistance is a ____ force 

Definition


Term
motor/rocket propulsion is a _______ force 

Definition


Term
elastic PE energy formula :
where there is kinetic energy
such as firing a spring loaded gun 

Definition
1/2mv_{1}^{2} + 1/2 kx_{12 }^{ }= 1/2 mv_{2 2}^{ }+ 1/2 kx_{2}^{2} 

