Physics Class II: Work/Energy, Torque, Circular Motion Flashcards
T/F: when the normal force is perpendicular to the distance object travels, it does NO work
True
because the cosine of angle between them is zero
what do we mean by saying that gravity is a conservative force?
it has a property that the total work done in moving an object between two points is independent of the path taken
springs and gravity have potential energy associated with them because________
they are conservative forces
what equation represents machanical advantage?
MA (mech. adv.)=Fout/Fin
Or, effort distance/resistant distance
equation for mechanical energy
MEnet=PE+KE
centripetal force equation
mv2/r
farther/closer? a mass is from the axis of rotation, the bigger the I (of the object) is
I = the resistance an object has to a change in its state of motion, equivalent to m in translational motion
farther
mechanical energy is conserved when:
(KE + PE)initial = (KE + PE)final
Happens when friction and air resistance do not affect the system
T/F: When friction and air resistance do not affect the system, then we can assume that all forces are conserved/conservative.
True
equation for torque
τ=F⋅rsin(θ)
translation is a word that signifies
distance
T/F in a conservative force, there is no energy loss d/t friction or heat
True
a system of pulleys is used to lift a 3000 N plank but only 500N of force is applied to lift it because of the pulleys. What is the mechanical advantage?
MA= Fresistance/Feffort
3000/500 = 6
notice how the weight of the object is the Fresistance
What is efficiency (η)
the efficiency of any machine measures the degree to which friction and other factors reduce the actual output of the machin from its theoretical maximum.
Efficiency (%) = Woutput/Energyinput
lower input energy = greater efficiency
what are the possible equations if you have the variables m and v?
p= m x v
KE = 1/2 mv2
