MOTION Motion Motion is when an objects distance
MOTION
Motion Motion is when an object’s distance is changing from another object. Displacement: the amount of change in motion Reference point: places or objects used for comparison to see if an object is in motion We measure the way objects move in meters and seconds (over distance and time)
Displacement xi displacement xf Consider a train moving along a track – this is an example of one-dimensional motion The train starts at an initial position, xi, and ends at a final position, xf. The change in position is called the displacement
Displacement yf ∆y = yf - yi xi ∆x = xf - xi xf yi ∆ = delta = “change” Displacement = final position – initial position *Important formulas
Displacement Negative displacement 10 m 30 m xf-xi = 10 m-40 m = -30 m Positive displacement 50 m 70 m xf-xi = 70 m-40 m = 30 m Displacement can either be positive or negative
Displacement x 1 x 2 x 3 = xf 10 m 30 m 50 m 70 m Displacement = 50 m-10 m = 40 m Distance = 20 m+40 m+20 m = 80 m Displacement does NOT always equal distance traveled
Displacement – Check for Understanding A person runs 4 laps around a track. What’s their displacement? Distance? Start/stop Displacement = 0 Distance = 1600 meters
Displacement – Check for Understanding 22 km 35 km What is the total displacement and distance if you… 1) Go from home to school 2) Ditch school and go to the beach, then run home to tell your parents how much you learned at school today 3) Forget school, just go straight from home to the beach, and then back home
Speed is the rate of distance covered over a period of time Measured in meters per second Describe the speed of the balls Do the balls ever have the same speed? Comparing speed: Motion of balls is from left to right. Ball A moves at constant speed. Ball B starts off faster than A and slows down. There are two passing points.
Velocity Average velocity is the speed and direction of an object over a time interval average velocity = change in position = change in time interval displacement time Instantaneous velocity is the speed and direction of an object at a single moment in time (instant) – no formula
Example During a race on level ground, Andrea runs with an average velocity of 6. 02 m/s to the east. What is Andrea’s displacement after 137 s? D v = 6. 02 m/s t = 137 s U ∆x = ? F = (6. 02 m/s)(137 s) = 825 m to the east A S
Velocity vs. Speed Velocity tells you the direction and how fast you’re going, whereas speed only tells you how fast you’re going v = displacement time s = distance time
Velocity – Check for Understanding 1) 2) 3) Does the speedometer on a car read the car’s average velocity or instantaneous velocity? If the speedometer of your car reads a constant speed of 40 km/hr, can you say 100% for sure that the car has a constant velocity? You drive around a race track at 28 mph and end up at the starting point. What was your average velocity for the trip?
Graphing Velocity is shown as an object’s position at specific times along its path Slope of a Line Average Velocity
Graphing Velocity Object 1 has positive velocity Object 2 has 0 velocity Object 3 has negative velocity Instantaneous velocity is shown as a tangent line
Real Life Example Jamaica’s Usain Bolt, hailed as the fastest man in the world, dominated the 200 m race in the Olympics with a time of 19. 32 s. What was his average velocity? Express your answer in miles per hour. v=? D t = 19. 32 s U ∆x = 200 m F = (200 m)(19. 32 s) = 10. 35 m/s A
Real Life Example Jamaica’s Usain Bolt, hailed as the fastest man in the world, dominated the 200 m sprint in the Olympics with a time of 19. 32 s. What was his average velocity? Express your answer in miles per hour. 10. 35 m 1 km 1 s 1000 m 1 mi 60 s 1. 6 km 1 min 60 min = 37260 mi 1 hr 1600 hr A = 23. 29 mph towards the finish line S
ACCELERATION Acceleration is not just a change in velocity, it’s how fast that change happens.
Acceleration Def. : Change in velocity � �Can be change in speed or direction �(speed up, slow down, or change direction) Acceleration = ∆v/ t �∆v = vf – vi �
Which cars are accelerating? A B C Cars B and C!
Which car has the greatest acceleration? A B C Car C!
CHECK FOR UNDERSTANDING Is this ball accelerating? Yes! Because the direction is changing.
ACCELERATION To measure it, you must know the initial velocity, the final velocity, and the time it takes to make the change.
ACCELERATION Acceleration = change in velocity time v a= t The unit for acceleration 2 is m/s.
ACCELERATION v is the difference between the final velocity (vf) and the initial velocity (vi). v = vf - vi
Example 1 A roller coaster’s velocity at the top of a hill is 10 m/s. Two seconds later it reaches the bottom of the hill with a velocity of 26 m/s. What is the acceleration of the roller coaster?
Answer v = 26 m/s vi = 10 m/s t=2 s �Acceleration = ∆v/ t �a = 26 m/s – 10 m/s 2 s a = 16 m/s 2 s a = 8 m/s/s or 8 m/s 2 � f
Examples 2 -4 – Try them! 2. A car travels at 60 miles per hour around a curve. Is the car accelerating? 3. A car travels in a straight line at 60 mi/hr. Is the car accelerating? 4. A car goes from 0 mph to 60 mph in 6 seconds. What’s the car’s acceleration?
Answers: 1. Yes! Because it’s changing direction. 2. No! It’s not changing speed or direction. 3. -vf = 60 mph vi = 0 mph t=6 s -a = vf – vi t -a = 60 – 0 mph = 10 m/s 2 6 s
Graphing Velocity vs. Time Constant acc. No acc. Increasing acc.
Graphing Speed Constant speed No motion Increasing Speed
Examples In your notes, describe the motion of the following race. Discuss the movement of each leg of the relay and include the terms, velocity, speed, acceleration, deceleration, rest. http: //www. youtube. com/watch? v=uw. LDpcye. VM
Independent Practice In your seat, quietly work on the worksheets Turn it into the inbox when you are finished. If you do not finish, it is your homework.
Close 1. 2. If Isaiha is skateboarding at a constant speed of 6 m/s and Jonathon is travelled 350 meters in a minute. Who is faster? If Isaiha accelerates over 5 seconds for 10 meters and Jonathon accelerates 6 seconds for 10 meters, who is faster?
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