Kinematics & Energy Flashcards
Power =
= work/time
= ΔKE/time
= forcecosθ*velocity
Work =
= ΔKE
= Fdcosθ
= power*time
ΔKE =
= ½ mv^2
Is momentum conserved if the object is acted on by external forces?
no
Gravitational force between 2 masses?
= GMm/r^2
circumference =
= πd
Distance and speed are both ______, meaning they represent _______ but not _______ and can never be _____.
Scalar
magnitude but not direction
can never be negative
Δx =
projections
Δx = v0t + ½at^2 Δx = ½v0t + ½vt
v^2 =
projections
v^2 = v0^2 + 2aΔx
v =
projections
v = v0 + at
At the apex of a projection, v= ? and a= ?
v = 0 a = g
Horizontal component of velocity =
v*cosθ
Vertical component of velocity =
v*sinθ
If initial and final elevations are the same, Δx =
Δx = (v0^2/g)* sin2θ
ΔPE =
mgh
total mechanical energy =
PE + KE
Other than in nuclear fusions, total energy is always _______
conserved
energy/work dissipated by friction
– µkmgL
Newton’s 1st Law
constant velocity continues indefinitely if net force = 0
Newton’s 2nd Law
f=ma
Newton’s 3rd Law
equal & opposite force
Ff=
Ff = µ*Fnormal
How do scales measure weight?
by finding the normal force
If an object is suspended and not moving, what can you say about the forces?
Horizontal components must be equal & opposite
Vertical components must be equal & opposite
the work done by centripetal force on any object moving in a circle is _____
0
W=Fdcosθ, since F is towards center of circle and d is traveling tangential to circle, they are always perpendicular to each other, and cos90º=0
Torque =
= Frsinθ
r = distance to fulcrum
to calculate torque when mass is distributed uniformly, position torque at the ____________
center of mass
If an object is in rotational equilibrium, what can you say about the torque?
torque clockwise = torque counterclockwise
Angular momentum L = ?
L = mvR
what are 2 examples of non conservative forces?
air resistance
friction
Efficiency =
energy out / energy in
moment of inertia =
tendency to resist angular acceleration/torque needed to rotate
what does a higher moment of inertia mean?
high kinetic energy
density of a human is proportional to ______ (using weight in air and water)
Wair/(Wair-Ww)
average velocity =
Vavg = (v0 + v)/2
