# Physics. For scalar quantities just look at the magnitude Ex: Speed For vector quantities you have to consider direction and magnitude Ex: Velocity and.

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Physics

For scalar quantities just look at the magnitude Ex: Speed For vector quantities you have to consider direction and magnitude Ex: Velocity and Acceleration

Speed is… Total distance traveled/ Δt YumaEckle y Wray 14 miles in 10 minutes 27 miles in 23 minutes

Speed is… Total distance traveled = 27 + 14 = 41 miles Total Time = 33 minutes = 0.55 hours Speed = 41 miles / 0.55 hrs = 75 mi/hr YumaEckle y Wray 14 miles in 10 minutes 27 miles in 23 minutes

Velocity is… the change in distance (Δd) / Δt YumaEckle y Wray 14 miles in 10 minutes 27 miles in 23 minutes

Velocity is Δd = 13 miles East Δt = 41 minutes = 0.55 hrs V = 13/ 0.55 = 24 mi / hr EAST YumaEckle y Wray 14 miles in 10 minutes 27 miles in 23 minutes

Calculate the speed and velocity of the following… A trackster who runs 2 complete laps on a track (0.5 mi) in 3 minutes (0.05 hrs) Speed = Velocity = 0.5/0.05 = 10 mi/hr 0.0/0.05 = 0 mi/hr A trackster who runs 2.5 complete laps on a track (0.625 mi) in 3.5 minutes (0.0583 hrs) Speed = Velocity = 0.625/0.0583 = 10.72 mi/hr 0.125/0.0583 = 2.14 mi/hr

Acceleration is a change in velocity over a change in time It is a VECTOR quantity Acceleration in the direction of movement speeds up an object Acceleration that is in the opposite direction of movement slows down an object Deceleration

Negative Acceleration that opposes the direction of movement…deceleration Positive Acceleration in the direction of movement Negative Acceleration and then Positive Acceleration

Velocity vs. Time Graphs Average Acceleration =ΔV/Δt -Units = m/s 2 Instant Acceleration -tangent line to a specific point -In this example Average Acceleration = Instantaneous Acceleration -Units = m/s 2

What is the Instantaneous Acceleration at… 1.5 seconds 6.5 seconds 2.5 seconds Slope = 0 = acceleration Slope = (2 m/s)/ 1 s = 2 m/s 2 = acceleration Slope = (-2 m/s)/ 1 s = -2 m/s 2 = acceleration

1-2 seconds 2-7 seconds 1-3 seconds = (1-1 m/s) / 1 s = 0 m/s 2 = (3-1 m/s) / 2 s = 1 m/s 2 = (2-1 m/s) / 5 s = 0.2 m/s 2 What is the Average Acceleration from…

0-6 seconds 1 second 8-10 seconds = (30-10 m/s) / 6 s = 3.3 m/s 2 = (10-60 m/s) / 2 s = -25 m/s 2 What is the Average Acceleration from… What is the Instantaneous Acceleration at… 8.5 seconds Slope = (40 m/s)/ 2 s = 20 m/s 2 = acceleration Slope = (-40 m/s)/ 1 s = - 40 m/s 2 = acceleration

A car travels for 10 seconds. What is the final velocity of a car with an initial velocity of 10 m/s and an acceleration of 20 m/s 2. Acceleration = ΔV/Δt = (V final – V initial )/ (t final – t initial ) V final = ??? V initial = 10 m/s Δt = 10 s Acceleration = 20 m/s 2 20 m/s 2 = (V final – 10 m/s)/ (10 seconds) 10 seconds*20 m/s 2 = (V final – 10 m/s) 200 m/s = (V final – 10 m/s) 200 m/s + 10 m/s = (V final ) 210 m/s = V final

Velocity vs TimeAcceleration vs Time

Chapter 3 Problems 54, 59, 60, 80, 82, 86a

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