physics 2 Flashcards
What is static vs dynamic equilibrium?
static- objects at rest
dynamic - objects moving at constant velocity
both - net force experienced by object is zero
If an object is “stationary” or exactly “balanced”, they are in ___
equilibrium
What is the formula for Torque? Torque for gravity?
T= Fl or T= Frsin(theta)
gravity - T= mgl
F - force
l - lever arm
r- distance between the force and point of rotation
In what specific situations should you use T= Frsin(theta)?
The force applied is not perpendicular to r. In most fulcrum and board-string problems the forces do act at 90 , hence sin(90 ) = 1 and T = Fr.
How to solve fulcrum and boards on strings problems?
set Tclockwise = Tcounterclockwise. Be sure to include all torques, including the torque created by the mass of the board
What is the definition of systems NOT in equilibrium?
Any problem where the object in question has a non-zero acceleration, or net force, is a non- equilibrium problem
How to solve for systems not in equilibrium?
by setting the sum of the opposing forces equal to one another (FLeft = FRight ; FUp = FDown) but then add the term “ma” to the weaker side.
How to solve for equilibrium on an inclined plane?
The force down the plane due to gravity is always given by F = mgsin(theta). The force of friction is always parallel to the plane, but opposite the direction of the sliding motion. There will never be an acceleration perpendicular to the plane, so you can ignore these forces. After you have accounted for all possible forces, set the sum of the “down forces” equal to the sum of the “up forces” and solve for the unknown.
What is energy?
the capacity to do work
What is the formula for Kinetic energy?
KE= 1/2(mv)^2
What is the formula for gravitational potential energy?
–Gmm/r or mgh
What is the formula for elastic potential energy?
1/2kx^2
What is the formula for the electrical potential energy?
Kqq/r or qEd or qV
What is the formula for potential energy stored by a capacitor?
1/2QV or 1/2CV^2 or 1/2Q^2/C
What is internal energy?
The energy of the internal vibrations and random motions of atoms and molecules within a system. When non-conservative forces, such as friction or drag, act on a moving object they cause the conversion of some kinetic energy into internal energy.
What is heat and chemical energy?
heat - energy dissipated as heat
chemical - energy contained within chemical bonds, or energy stored/released due to the separation and/or flow of electrons
What is the formula for mechanical energy?
ME = KE + PE
In the absence of non-conservative forces such as friction, drag, air resistance, ____ is always conserved
mechanical energy
Name the type of energy possessed or created by: an explosion
Chemical energy turns into heat energy and the kinetic energy of any flying debris
Describe the energy transformations that take place as a rocket ignites, combusts its rocket fuel, launches into the air, rises to its maximum height, falls back to earth, and strikes the ground.
Chemical energy stored in the bonds of the rocket fuel is transferred into kinetic and gravitational potential energy as the rocket rises. If air resistance is taken into account some energy will also be dissipated as heat due to drag. Gravitational PE reaches a max at the max height and is then transferred back into kinetic energy (and heat if considering air resistance) as the rocket falls back to earth. When the rocket strikes the ground its kinetic energy is transferred into heat energy.
What is the Law of Conservation of Energy?
Energy is frequently transferred back and forth between forms, but never lost
What is an open, closed, and isolated system?
open - both mass and energy can be exchanged w the surroundings
closed - energy, but not mass can be exchanged
isolated - neither mass or energy can be exchanged
If energy is changed, think ____
WORK
1) Change in velocity (change in KE = work; this is the most common example)
2) Change in height (change in gravitational PE = work)
3) Change in position of masses/planets/etc. in space (change in gravitational PE = work)
4) Change in position of a charge (change in electrical PE = work)
5) Compression of a spring (change in elastic PE = work)
6) Friction (change in internal energy = work)
7) Air Resistance (change in internal energy = work)
What is the second way you should think of work?
W = Fdcosθ or Favgd