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Motion & Speed. Ch. 3. Motion & Speed. What is motion? 1. Changing one’s position 2. Moving from one place to another 3. You need a reference point to know if a position has changed. Motion & Speed. Example: You look out the window and the mail truck is parked by the mailbox.
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Motion & Speed Ch. 3
Motion & Speed • What is motion? 1. Changing one’s position 2. Moving from one place to another 3. You need a reference point to know if a position has changed.
Motion & Speed • Example: • You look out the window and the mail truck is parked by the mailbox. • One minute later you see it down the block. • Even though you didn’t see the motion you know it moved because it’s position relative to the mailbox has changed.
Motion & Speed • Example: • The earth’s crust is constantly in motion, but you can’t see it move. • We know it moves because it’s position changes relative to our point of reference – the sun.
Motion & Speed • Changing Motion 1. Speed – the distance you are going divided by the time. S =
Motion & Speed Distance (miles, km, m) D S T Speed Time unit of distance unit of time m/s, km/hr (s, min, hr)
Motion & Speed • Example: A car is traveling at a speed of 100 m/s. How far will it get in 35 seconds?
Motion & Speed 2. Average speed – total distance / total time -Used when speed varies
Motion & Speed • Example: You set out to ride your bike. You start at 0 km/hr and increase to 20 km/hr. You then slow to 12 km/hr and come to a stop at a red light. The light changes and you speed up to 35 km/hr. It took you a total of 15 minutes to ride your bike a total distance of 5 km. What is your average speed?
Motion & Speed • Example:
Motion & Speed 3. Instantaneous speed – your rate of motion at any time -Speed shown by your speedometer