Chapter 7: Kinetic + Work (Exam 3) Flashcards
What is kinetic energy?
Energy in motion
What is potential energy?
Energy at a position (rest)
What is the variable for kinetic energy?
K
K =
1/2mv^2
What are the units for K?
1kg m^2/s^2 or joule (J)
What is the definition of work?
transfer of energy through a force
What sign (+/-) is work?
BOTH! either + or -
What is the variable for work?
W
W =
delta K = Kf-Ki
What is the expanded delta K equation?
1/2mvf^2 - 1/2mvi^2
If vf > vi and Kf > Ki, what is the sign of W?
+ (positive)
In the ABcos(x) equation, what are the corresponding angles and signs of work?
theta > 90 degrees: w = negative (-)
theta < 90 degrees: w = positive (+)
theta = 90 degrees: w = 0
What is the equation for multiple forces?
sigma F = F1 + F2 + … + Fn
What is the equation for W using forces?
F1d + F2d + … + Fnd
What is the equation for K using work?
delta K = W = W1 + W2 + … + Wn
What is the equation for work done by weight?
Wg = mgdcos(x) = ± mgd
What is the equation for work using integrals?
integral (xi to xf) F(x) dx
What is Hooke’s Law?
Fs = -kx
What is k?
spring constant
What is the unit for k?
N/m
What is the equation for Ws? (Hooke’s Law)
Ws = integral (xi to xf) [Fs dx] = -k integral (xi to xf) [x dx] = -1/2k(xf^2-xi^2)
What is the variable for power?
P
What is the equation for average power?
W/delta t
What are the units for average power?
J/s or watt (w)
What is the equation for power?
dW/dt
Pv =
Fvcos(x)
F(x) =
ma
What is the equation for work using mass and acceleration?
w = integral (xi to xf) F(x) dx = integral (xi to xf) ma dx = integral (vi to vf) mv dv
ma dx =
m(dv/dt) dx = m(dv/dx) dx = mv dv
dv/dt =
dv/dx = dx/dt = dv/dx v
overall, w =
delta K
