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M OTION

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Motion is a change in position To determine a change in position you need a reference point, a point that is assumed to be stationary. The reference point is used to create a frame of reference, a coordinate system in which the position of objects are measured.

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D ISTANCE AND D ISPLACEMENT Distance is the total length traveled by an object. It is always positive. Distance does not have to be in a straight line. Displacement is the distance and direction away from the starting point. It can be positive or negative. Displacement must always be in a straight line. B=10 km C = 20 km A=30 km

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M OVEMENT We measure how far an object has moved, or its distance, in meters

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M OTION Motion includes three things: Distance Time Speed Speed is the distance an object travels per unit of time. Speed = distance/time or s=d/t The standard unit for speed is m/s or meters per second

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E XAMPLE A train traveling at a constant speed travels 800 meter in 100 seconds. How fast is the train moving?

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E XAMPLE 1 speed= d/t d=800 m t=100s speed=800m/100s speed = 8 m/s

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E XAMPLE 2 A man runs at a constant speed of 10 m/s. How long does it take him to run 40 meters?

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E XAMPLE 2 speed= d/t t=d/s d=40 m s=10m/s d=40 m/10 m/s t = 4 s

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C ONSTANT VS. A VERAGE S PEED Speed is ususally not constant. It can vary over the distance travelled. Average speed describes the motion of an object when the speed is changing. Average speed is equal to the total distance divided by the total time. Instantaneous speed is the speed of an object at a certain point in time.

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V ELOCITY Velocity is the speed of an object and the direction of its motion. v av = d / t = (d f - d i ) / (t f - t i ) - change in value The difference between average speed and average velocity is the addition of a direction. Bill was travelling at 60 miles per hour. SPEED Bill was travelling north at 60 miles per hour VELOCITY

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M EASURING M OTION A speedometer gives the instantaneous speed of a vehicle. The cruise control of a car helps to maintain a constant speed.

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G RAPHING M OTION A distance/time graph displays the motion of an object over time meters seconds The height of a point on the graph is how far it has travelled from the origin point. The slope of a line is the speed. The steeper the line the faster the speed. The average speed is the slope of the line connecting the starting and ending points

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V ELOCITY M INI -L AB Mark your starting point on the floor with tape At the starting point one member will give the car a gentle push. At the same time, another member will start the stopwatch. Stop timing when the car comes to a complete stop. Record the time. Mark the spot at the front of the car with a pencil. Use a meterstick to measure the distance traveled. Write down this number in meters. Calculate the speed of the car. Repeat the process 4 times Next, once the car starts have the timer start and call out every second for 5 seconds have the other group memebers mark where the car is with their hand. Measure where the car was and plot the informaion on a graph.