Chapter 2: Work and Energy Flashcards
Kinetic energy formula?
KE = 1/2mv^2
Where v is speed, not velocity
Gravitational potential energy formula?
PE = mgh
where the variables are mass, acceleration due to gravity and height. PE also given as U
Elastic potential energy formula? (springs)
PE = 1/2kx^2
where k is the spring constant, x is the magnitude of displacement of the of the spring from equilibrium
What is total mechanical energy?
Formula?
Sum of an object’s potential and kinetic energies
E = PE + KE
Conservative vs nonconservative forces?
Cons = path independent and do not dissipate energy eg gravity and electrostatic interactions Noncons = Dissipate energy, eg friction, air resistance
Conservation of mechanical energy formula?
delta E = delta PE + delta KE = 0
Work done by nonconservative forces formula?
W_nonconservative = delta E = delta PE + delta KE
What is work? Formula? Units?
The process of transferring energy from one system to another
W = F. d = Fd cos theta
where F is the magnitude of the applied force, d is the magnitude of displacement through which the force is applied and theta is the angle between the applied force vector and the displacement vector
- Joules
Work on a P-V graph?
Equal to the area under the curve
What is power? Formula? Units?
The rate at which energy is transferred from one system to another
P = W/t = delta E/t
Where P is power, W is work (which is equal to the change in energy) and t is time
-watts, which is J/s
Work-energy theorem equation?
W_net = delta KE = Kf - Ki
What is mechanical advantage? Three commonly tested simple machines?
the ratio of magnitudes of the force exerted on an object by a simple machine (Fout) to the force actually applied to the simple machine (Fin)
= Fout/Fin
Pulleys, levers and inclined planes
How do pulleys provide a mechanical advantage. Rope displacement?
Half of the tension is on the support rope, so only half the force is required, but the rope must be pulled twice the length of the displacement
Simple machine efficiency formula?
Efficiency = Wout/Win = (load)(load distance)/ (effort)(effort distance)
