Physics_50_Midterm_x2_Study_Guidex10xPDF

# Physics_50_Midterm_x2_Study_Guidex10xPDF - Physics 50"Study...

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Physics 50 "Study Guide" for Midterm #2 ("Laundry List" of important concepts) by Todd Sauke Concept (important concepts in bold; vectors also shown in bold ) Symbol or Equation We use the international SI system of units which employs the meter (m) kilo (k)=10 3 mega (M)=10 6 for length, the kilogram (kg) for mass, and the second (s) for time milli (m)=10 -3 micro ( μ )=10 -6 Trigonometry : We use sine , cosine , and tangent functions to relate sin( θ) = h o /h θ = sin -1 (h o /h) angles to the ratios of various lengths of the sides of right triangles cos( θ ) = h a /h θ = cos -1 (h a /h) Angles can be measured in radians (2 π rads per circle) or in degrees tan( θ ) = h o /h a θ = tan -1 (h o /h a ) (360 ˚ / circle). Set your calculator correctly. h 2 = h o 2 + h a 2 (Pythagoras) Physics quantities are either scalars or vectors (magnitude & direction) | v | = a positive scalar, "v" Unit vectors give only directional information, eg. î for x-axis, ĵ for y (scalar) * ( unit vecto r) = vector When adding vectors , think of the vectors' components separately components of vectors add Scalar product ("dot product") of two vectors gives a scalar result A B = A B cos ( φ ) Vector product ("cross product") of two vectors gives a vector result | A x B | = A B sin( φ ) The direction of the cross product vector is perpendicular to both A & B; given by right-hand-rule (RHR) The position vector r of a point P is the vector from the origin to P r = x î + y ĵ + z ǩ Kinematics describes motion. Dynamics deals with effect of forces on motion Δ r = r r 0 Δ t = t – t 0 Average velocity: v ave = Δ r / Δ t . Instantaneous velocity: v = lim( Δ t Æ 0) Δ r / Δ t . speed (scalar); velocity ( vector ) Average acceleration: a ave = Δ v / Δ t . Instantaneous acceleration: a =lim( Δ t Æ 0) Δ v / Δ t . time (scalar);acceleration ( vector ) Speed is different from velocity. Speed is the (positive) magnitude of velocity We use 6 kinematic variables: [x (or y), x 0 (or y 0 ), v x (or v y ), v x0 (or v y0 ) , a x (or a y ) and t] label directions '+' & '-' on diagram Constant acceleration: make a table of known (or implied) kinematic variables v = v 0 + a t x-x 0 = ½(v 0 +v) t and select the equation here involving those variables and the target variable. v 2 = v 0 2 + 2a (x – x 0 ) In two (or three) dimensions, apply the x, y (or z) equations separately x = x 0 + v 0 t + ½ at 2 Projectile motion: an object flies freely through the air, accelerated only by gravity a y = -g = -9.8 m/s 2 (projectile motion) The Quadratic Formula comes in handy: for a x 2 + b x + c = 0 Æ x = (-b ± b 2 – 4ac ) / (2a) Velocity of object A relative to object B is written v AB (note order of subscripts) v AC = v AB + v BC v BA = - v AB Acceleration component parallel to v changes the speed of the object Acceleration component perpendicular

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## This note was uploaded on 09/08/2010 for the course PHYS 50 at San Jose State.

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Physics_50_Midterm_x2_Study_Guidex10xPDF - Physics 50"Study...

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