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MSTC Physics C. Chapter 1 and 2 Review Vectors, Velocity, Acceleration. Scalar Quantity. Quantity that can be completely described with a number ex – time temperature mass speed. Vector Quantity. Quantity that has to be explained with a number and a direction
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MSTC Physics C Chapter 1 and 2 Review Vectors, Velocity, Acceleration
Scalar Quantity • Quantity that can be completely described with a number ex – time temperature mass speed
Vector Quantity • Quantity that has to be explained with a number and a direction ex – force displacement velocity
Displacement • Change in position of an object A B
Distance(Path Length) • Length of the path taken between 2 points A B
Question What condition(s) must be met for two vectors to be equal? same magnitude and direction
Question How do you subtract two vectors? add the opposite of the one subtracting from the first vector A – B = A + ( - B )
Adding Vectors Graphically A B To find R = A + B add the vectors head to tail The resultant goes from where you started to where you stopped
Adding Vectors Via Components A has Ax= Aand Ay = 0 B has Bx= Bcos30 and 30 By= Bsin30 Σx = Ax + Bx= A + Bcos30 Σy= Ay + By= 0 + Bsin30 and R= √ x2 + y2 tanΘ = y/x
Unit Vector • Dimensionless vector one unit in length used to specify a given direction • i,j, k A A = Axi + Ayj
Example Find the sum of A and B where A = 2i+ 2jand B = 2i – 4j.
Example A hiker walks 25 km SE and then 40 km at 60 degrees N of E. Determine the hiker’s total displacement.
Average Velocity • Ratio of displacement to the corresponding time interval • Independent of path taken • Gives no details about motion • Slope of x vs t graph vavg= Δx / Δt
Instantaneous Velocity • Limiting value of the ratio Δx / Δt as Δt approaches zero • Slope of tangent line for an x vs t graph • Derivative of the position function evaluated at a specific moment in time
Average Acceleration • Ratio of the change in velocity to the corresponding time interval • Slope of a velocity vs time graph aavg = Δv / Δt
Instantaneous Acceleration • Limit of average acceleration as Δt approaches zero • Slope of tangent of v vs t graph • Derivative of the velocity function evaluated at a specific moment in time
Kinematic Equations • Set of equations that can help describe motion • Can only be used if acceleration is constant v = vo + at x = vot + ½ at2 x = ½ (vo + v )t v2 = vo2 + 2ax
Example A car traveling at a constant speed of 30 m/s passes a trooper hidden behind a billboard. One second after the speeding car passes, the trooper sets in chase with a constant acceleration of 3 m/s2. How long does it take the trooper to overtake the speeding car?