AP Physics Midterm Review

• average velocity


  displacement / change in time(△x/△t)
• instantaneous velocity


  lim of displacement / change in time
• average speed


  total distance / time
• average acceleration

  change in velocity / change in time(△v/△t)
• instantaneous acceleration


  lim of change in velocity / change in time
• speeding up


  v and a have same sign
• slowing down

  v and a have opposite signs
• position from velocity equation

  integral from x initial to x final of v(t)
• 1-D Kinematic Equations (given on equation sheet)


  v = v0 + atx = x0 + v0t + 1/2at^2v^2 = v0^2 + 2a(change in x)

  
• free fall


  motion of an object exclusively under the influence of the force of gravity
• 3 possibilities for 1-D free fall

  If +y is upward:object dropped from rest (v0 = 0)object thrown downward (v0 = negative)object thrown upward (v0 = positive)
• plots of position and velocity v time with differing accelerations

  
• expression for vector A in terms of x and y components

  vector A = (A cos x)i + (A sin x)jwhere A is the hypotenuse of triangle made by vector A's x and y components
• magnitude of vector A


  A = √(Ax)^2 + (Ay)^2
• Componentwise Addition of Vectors (C, A, B)


  Cx = Ax + BxCy = Ay + By

  
• 2-D Kinematics General Equations

  r(t) = x(t)i + y(t)jch. r = (ch. x)i + (ch. y)javerage velocity vector = (ch. x/ch.t)i + (ch. y/ch.t)jinstantaneous velocity vector = (vx)i + (vy)j = (dx/dt)i + (dy/dt)jinstantaneous acceleration = (ax)i + (ay)j = (d^2x/dt^2)i + (d^2y/dt^2)j
• In 2-D projectile motion w constant a: horizontal component of the initial velocity (vx0)

  vx0 = v0 cos x
• In 2-D projectile motion w constant a: vertical component of the initial velocity (vy0)

  vy0 = v0 sin x
• In 2-D projectile motion: horizontal component of the acceleration (ax)


  ax = 0
• In 2-D projectile Motion: vertical component of the acceleration (ay)


  ay = -g
• In 2-D projectile motion w constant a: vertical component of velocity (vy) at maximum height

  vy = 0
• 2-D Kinematic Equations for Horizontal Component of Projectile Motion

  vx = v0 cos x (constant)ch. x = (v0 cos x)t
• 2-D Kinematic Equations for Vertical Component of Projectile Motion

  vy = v0 sin x - gtch. y = (v0 sin x)t - 1/2gt^2
• mechanical equilibrium


  object has constant velocity and zero acceleration
• mass


  a measure of an object's resistance to changes in velocity(lower mass means more susceptible to changes in velocity)
• force


  push or pull, nonzero net force causes an object to accelerate(If m1 > m2, a1 < a2)
• Newton's First Law

  In absence of a net force, object at rest will remain at rest and an object in motion will continue to move in the same direction at the same speed
• Newton's Second Law

  F = ma
• Newton's Third Law

  The force that A exerts on B is equal in magnitude and opposite in direction to the force that B exert on A
• Relationship between the coefficients of static and kinetic friction


  us > uk
• How to determine which way friction vector points


  ask how the object would move in the absence of friction
• uniform circular motion


  particle travels with constant linear speed (v) in a circular pathparticle's velocity vector is always tangent to the circular path
• magnitude and direction of acc. vector in UCM (given on equation sheet)


  a = v^2 / racc. vector points toward the center of the circle
• centripetal force


  not a new force but can be the force of tension, friction, gravitation, normal force, etc.
• Relationship between centripetal force and centripetal acceleration


  F = mv^2 / r
• Period of rotation (given on equation sheet)


  T = 2pir / v
• work (N * m)


  mechanism by which energy is transferred to an object via the application of a force while object undergoes displacement
• positive work


  F points in the same direction as displacement (facilitates motion)
• negative work


  F points in the opposite direction as displacement (opposes motion)
• power (W)


  the rate at which work is done