Understanding Motion Concepts for Physics Study

Measuring Motion Speed, Velocity, and Acceleration

Learning Targets 1: I can explain how to determine if an object is in motion. 2: I can differentiate between distance and displacement. 3: I can differentiate between speed and velocity. 4: I am able to manipulate and use speed and velocity formulas to solve problems. 5: I can define acceleration. 6: I can use and manipulate the formula for acceleration to solve problems.

What is Motion? Change in position in relation to a reference point or stationary object

Distance vs. Displacement Distance follows the actual path Displacement is always a straight line http://maps.google.com/maps?hl=en&q =Xenia&bav=on.2,or.r_gc.r_pw.r_qf.&bv m=bv.43148975,d.aWM&biw=1366&bih= 622&wrapid=tlif136235527620010&um=1 &ie=UTF- 8&sa=X&ei=TuQzUf6yD8vryAGCm4CYAQ &ved=0CAgQ_AUoAg

Speed Speed is the distance traveled divided by the time interval during which the motion occurred Normally, objects do not travel at a constant speed Average Speed - total distance total time D S T

Instantaneous vs. Average Speed

Speed Units Will always be a distance unit / a time unit Ex. Cars: mi./h Jets: km/h Snails: cm/s Falling objects: m/s

Calculating Speed What is the speed of a car that travels 30 miles in 2 hours? 15 mi/hr. How long will it take a car to go 220 miles traveling 55 mph? 4 hours If a car is traveling at 35 m/hr for 6 hours, how far will it travel? 210 miles D S T

Graphing Speed

Graphing Speed: Distance vs. Time Graphs Denver Phoenix

Graphing Speed: Distance vs. Time Graphs Speed = Slope = Rise/Run Rise

Different Slopes 8 7 Slope = Rise/Run = 0 km/1 hr = 0 km/hr 6 Distance (km) 5 Rise = 2 km 4 Run = 1 hr Rise = 0 km 3 Run = 1 hr 2 Slope = Rise/Run = 2 km/1 hr = 2 km/hr Rise = 1 km 1 Run = 1 hr 0 Slope = Rise/Run = 1 km/1 hr = 1 km/hr 1 2 3 4 5 6 7 Time (hr)

Velocity Velocity is the speed of an object in a particular direction Imagine two bicyclers leave the same building at the same time. The both cycle at 10km/hr for 5 minutes. Why don t they end up at the same place?

Calculating Velocity Same as speed, but also includes direction Example: A plane travels south at 540 miles/hour. Johnny walks 1 block/ minute towards the school D V T

Resultant Velocity The combination of two different velocities acting at the same time + = 15 m/s 1 m/s 16 m/s - = 14 m/s 15 m/s 1 m/s

Acceleration Acceleration is the rate at which velocity changes over time An object accelerates if its speed, direction, or both change Unit: m/s2 Average acceleration = final velocity starting velocity time it takes to change velocity V a T

Acceleration and Velocity As velocity increases, so does acceleration As velocity decreases, so does acceleration When direction changes, so does acceleration When there is a constant velocity, there is no acceleration Increasing velocity - positive acceleration Decreasing velocity - negative acceleration- deceleration

Acceleration and Velocity

Calculating Acceleration: Example A roller coaster s velocity at the top of a hill is 10m/s. Two sec later it reaches the bottom of the hill with a velocity of 26 m/s. What is the acceleration of the roller coaster? Vf-Vo T 26-10 2 8 m/s/s T a V

Velocity vs. Time Graph Slope is the acceleration. A straight line is constant acceleration 14 12 10 Speed (m/s) 8 6 4 2 0 0 1 2 3 4 5 6 Time (s)