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General Physics. Midterm Review. Definition of Physics. Study of Energy and matter. SI Units. Mass – kilogram Time – seconds Length – meter. Metric Prefixes. Kilo --- one thousand (1000) Hecto --- one hundred (100) Centi --- one hundredth (.01) Milli --- one thousandth (.001).
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General Physics Midterm Review
Definition of Physics • Study of Energy and matter
SI Units • Mass – kilogram • Time – seconds • Length – meter
Metric Prefixes • Kilo --- one thousand (1000) • Hecto --- one hundred (100) • Centi --- one hundredth (.01) • Milli --- one thousandth (.001)
Significant Digits • 10000 • 0.0000540 • 342.15 • 67.00 • 890.02
Significant Digits • Adding and Subtracting --- go by the lowest number of digits to the right of the decimal point • 67.03 – 7.045 =
Significant Digits • Multiplication and Division : go by the lowest number of sig. digits • (2.45 x 105)( 3.678 x 102)=
Conversions • 120 kg = ______ g • 54 km = _______ mm • 120 m/s = ______ km/hr • 53 cm = ______ m
Distance vs. Displacement • Distance: scalar, add total distance traveled • Displacement: vector, difference between starting and ending point
Distance vs. Displacement A person walks 10 m north, 5 m south, then 2 m north. What is the displacement? What is the distance traveled?
Graphs (General) • Slope = vertical change / horizontal change • Independent variable – manipulated by the experimenter, on the x-axis • Quadratic graph – Parabola, smooth upward curve, y is proportional to x2 • Inverse graph – hyperbola • Linear graph – straight line, y and x are directly proportional
Position-time graphs • Slope = velocity • Constant velocity: • Constant acceleration:
Position-time graph • At rest: • Slowing Down:
Velocity-Time Graphs • Slope = acceleration • Area under the curve = displacement • A = l x w • A =1/2bh • Constant velocity:
Velocity-time graphs • Constant acceleration:
Velocity • V = d/t
Acceleration • Change in velocity with time • a = Dv/Dt • Vf = Vi + at • d = vit + 1/2at2
WGUMCD • At max height, velocity is 0 • Vf = -Vi (Perfect Symmetry)
Free Fall • Distance is proportional to t2 • all objects accelerate at the same rate regardless of mass, if air resistance is ignored
Vectors • Resultant vector – the sum of more than one vector, placed from the tail of the first vector to the tip of the last vector • A student walks 7 m east and then 5 m south, what is the displacement? • Reverse the direction of the initial vector when subtracting
Component Method • X component = hcos • Y component = hsin
Newton’s First Law • Equilibrium – all forces on an object are balanced • Fnet = 0 • object is at rest or moving with a constant velocity
Newton’s Second Law • F = ma • Increase acceleration: decrease mass and increase Force • Weight: gravitational force exerted by a body • W=mg
Newton’s Second Law • A snowflake falls with a force of 5 N downward, and experiences a frictional force of 2 N upward. What is the net force on the snowflake? • What must the frictional force on the snowflake be to make it move with a constant speed?
Newton’s Second Law • A baseball player slides into secondbase with a force of 25 N and experiences a frictional force of 4 N. If the player has a mass of 60 kg, what is his acceleration?
Newton’s Third Law • For every action there is an equal and opposite reaction
Incline planes • Increasing the angle increases the acceleration and speed of an object • The parallel component of the force of gravity causes an object to slide down the incline plane • Fg = mg • Fg perpendicular = Fgcos • Fgparallel = Fgsin
Incline Planes • FN = -Fg perpendicular • Fric = µFN • Fnet= Fric + Fg parallel • a = Fnet /m
Projectile Motion (general) • Motion in the horizontal direction is independent of motion in the vertical direction • Velocity in the horizontal direction is constant
Type I Projectile Motion • dy= 1/2gt2 • dx= vxt • vfy = gt
Type II Projectile Motion • Range increases up to 450 (max range) and then decreases after that • Vix = Vi cos • Viy = Vi sin • Vfy = Viy + gt • dy = Viyt + 1/2gt2 • dx = vxt • Vf = - Vi