Motion and Acceleration Notes Chapter 2 Section 1 and 2

Key Terms Distance Distance How far an object has moved How far an object has moved Displacement Displacement The distance AND direction of an object’s change in position from the starting point The distance AND direction of an object’s change in position from the starting point Speed Speed The distance an object travels per unit of time The distance an object travels per unit of time s=d/t s=d/t

Key Terms  Average Speed Is the total distance traveled divided by the total time of travel Is the total distance traveled divided by the total time of travel Instantaneous Speed Instantaneous Speed Is the speed at a given point in time Is the speed at a given point in time Velocity Velocity Describes the speed and direction of an object Describes the speed and direction of an object Momentum Momentum The product of an objects mass and velocity The product of an objects mass and velocity Equation (p=mv) Equation (p=mv)

Motion Review What is the difference between motion and displacement? What is the difference between motion and displacement? Motion involves the change in position relative to a reference point and displacement involves the change in position AND the direction of the movement Motion involves the change in position relative to a reference point and displacement involves the change in position AND the direction of the movement

Speed Rate Rate Any change over time Any change over time Equation Equation Speed=distance/time Speed=distance/time A speed that doesn’t change over time A speed that doesn’t change over time Constant speed Constant speed A speed that DOES change A speed that DOES change Changing speed Changing speed

Speed How do constant speed and changing speed differ? How do constant speed and changing speed differ? At a constant speed, an object’s instantaneous speed remains the same, but at changing speed, an object’s instantaneous speed varies At a constant speed, an object’s instantaneous speed remains the same, but at changing speed, an object’s instantaneous speed varies Examples: Examples: Driving a car Driving a car

Speed Review Average Speed Average Speed Speed of motion when speed is changing Speed of motion when speed is changing Equation for Avg Speed Equation for Avg Speed Speed=TOTAL distance/TOTAL time Speed=TOTAL distance/TOTAL time Instantaneous Speed Instantaneous Speed Speed at any given point in time Speed at any given point in time

Velocity Vs. Speed Race Car animation Race Car animation Race Car animation Race Car animation

Calculations of Speed and velocity V D V T

Practice problem #1 An object travels 345 km in 6.5 hours. What is the speed of the object An object travels 345 km in 6.5 hours. What is the speed of the object

Practice Problem #2 A car traveling at 65 miles/hour completes a trip in 5.0 hours. How far did the car travel? A car traveling at 65 miles/hour completes a trip in 5.0 hours. How far did the car travel?

Practice Problem # 3 A boat is moving 65 km/hr and travels 60 km. How long did it take? A boat is moving 65 km/hr and travels 60 km. How long did it take?

Distance-time Graph Plot distance on a __________ axis Plot distance on a __________ axis Vertical Vertical Plot time on a ____________ axis Plot time on a ____________ axis Horizontal Horizontal Purpose Purpose To show the change in distance related to change in time To show the change in distance related to change in time

Distance-Time Graph Distance vs Time Distance (m) Time (s)

Units….. Speed Speed Miles/hour; miles/minute; km/s; m/s etc Miles/hour; miles/minute; km/s; m/s etc Time Time Second, minute, hour, days etc Second, minute, hour, days etc Distance Distance Miles, km, meters, cm etc Miles, km, meters, cm etc Acceleration Acceleration m/s 2 ; km/s 2, miles/second/second m/s 2 ; km/s 2, miles/second/second

ACCELERATION

Acceleration Definition Definition Change in velocity’s rate Change in velocity’s rate Positive acceleration Positive acceleration Speed is increasing Speed is increasing Negative acceleration Negative acceleration Speed is decreasing Speed is decreasing

An Object is accelerating… IF it changes speed OR direction IF it changes speed OR direction Example: Example: A car going 60 mph increases in speed to 70 mph as it gets onto the highway. Is it accelerating? A car going 60 mph increases in speed to 70 mph as it gets onto the highway. Is it accelerating? YES YES A car staying at a constant speed of 70 mph in a circle. Is it accelerating? A car staying at a constant speed of 70 mph in a circle. Is it accelerating? YES YES

Calculating Acceleration Equation Equation Change in velocity/time Change in velocity/time Change in velocity=final velocity-initial velocity Change in velocity=final velocity-initial velocity Unit for acceleration Unit for acceleration Meters per second squared (m/s 2 ) Meters per second squared (m/s 2 )

Calculations of Acceleration V V A T

The physics Classroom Acceleration Vs. Velocity Acceleration Vs. Velocity Acceleration Vs. Velocity Acceleration Vs. Velocity

Practice Problem #1 Falling objects drop with an average acceleration of 9.8 m/s/s (m/s2). If an object falls from a tall building, how long will it take before it reaches a speed of 49 m/s Falling objects drop with an average acceleration of 9.8 m/s/s (m/s2). If an object falls from a tall building, how long will it take before it reaches a speed of 49 m/s

Practice Problem #2 A bus moving at 25 km/hr comes to a stop in 10 seconds. What is its acceleration? A bus moving at 25 km/hr comes to a stop in 10 seconds. What is its acceleration?

Practice Problem #3 A driver starts his parked car and within 5 seconds reaches a velocity of 54 km/hr as he travels east. What is his acceleration? A driver starts his parked car and within 5 seconds reaches a velocity of 54 km/hr as he travels east. What is his acceleration?

Practice problem #4 If an airplane accelerates at 50 meters/second/second, how much does its speed change in 3 seconds? If an airplane accelerates at 50 meters/second/second, how much does its speed change in 3 seconds?