Chapter 7: Kinetic Energy & Work Flashcards
What is energy?
It is a quantity that specifies important information about the state of a system–notably, the ability of the system to cause change in physically measurable properties of its environment.
SI unit: joule (J) = kg * m^2/s^2 = n * m
Is energy a vector quantity?
No! It is a scalar quantity!
Energy comes in three basic forms: ___, ___ and ___.
Kinetic energy; potential energy (gravitational, elastic, electrostatic); rest energy.
Energy can be transformed from one form to another, and the total energy of a closed system (can)/(cannot) change.
Cannot
What is kinetic energy?
The energy a particle has because of its motion. K = 1/2 * m * (V(subx)^2 + V(suby)^2 + V(subz)^2)
What is work?
The transfer of energy between a system and its surroundings by means of a force.
Work is done by a ___.
Force
Work done by a constant force is:
W(subf) = F(arrow) * Δr
Is work a vector quantity?
No! It is a scalar quantity.
When work is done by the ___ forces acting on a particle, energy is transferred to or from the particle.
External
W(net) = …
ΔK = K(sub2) - K(sub1)
If W(subnet) > 0, then ΔK ___ 0.
>
If W(subnet) < 0, then ΔK ___ 0.
<
If W(subnet) = 0, then ΔK ___ 0.
=
TRUE or FALSE: Forces perpendicular to the motion of the object do work.
False! They do no work.
Work done by the gravitational force is demonstrated by the formula W(subgrav) = …
-mgΔy
Work done by gravity (is affected by)/(is not impacted by) horizontal distance traveled.
Is not impacted by
What is Hooke’s Law?
F(subs) = -kΔx
The SI unit of the spring constant K is…
N/m
A larger value of K means a ___ string.
Stiffer
You can use F(subs) = -kΔx as long as the equilibrium position is ___.
The origin
When the work done by the spring constant isn’t constant, you (can)/(cannot) use the standard formula for work.
Cannot
Use either ___ or an ___ to get the area under the curve on a graph of ___ vs. ___ to get the work for a specific distance.
Summation; integral; force; distance.
On a frictionless banked curve, F(subn) supports (more)/(less than) the weight of the object, meaning F(subn) ___ mgcosθ.
More; >
When there is no friction on a banked curve, ___, or ___. This is because the normal force on a banked curve has to support the entire weight of the object and provide the centripetal force necessary to keep it in motion.
F(subny) = mg; F(subny) = F(subn)cosθ = mg
If there is not friction, there is a(n) (exact speed)/(range of speeds) where an object will not slip and move up or down the incline.
Exact speed
On a banked curve WITH friction, the setup for the equation is the same as without it–except, this time, a friction force directed (up)/(down) the incline, with magnitude ___, must be factored into the equation.
Down; μF(subn)
What is power?
The work done over a set time interval.
SI unit: Nm/s = J/s = W (watt)
Instantaneous power due to applied force is:
P(subF) = F(arrow) * v(arrow)
