# Matter in Motion Chapter 1.1 pp. 4-10. Motion How do we know something is moving? Is this guy in motion? How do you know?

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Matter in Motion Chapter 1.1 pp. 4-10

Motion How do we know something is moving? Is this guy in motion? How do you know?

Measuring Motion Must observe motion in relation to another object Reference Point = an object that appears to stay in place in relation to an object being observed for motion (earth surface, tree, etc.)

Motion Motion = object changing position over time when compared to a reference point Two elements: position and time

Speed How do we know an object’s speed? It depends on two factors: distance and time distance and time Speed = rate at which an object moves Ave speed = total distance/total time

Speed on a graph

Velocity What if I said “Johnny left CCMS and walked 1 mile” Can you know where he ended up? Why or why not? Velocity = speed of an object in a particular direction Changes when SPEED or DIRECTION changes Sometimes can combine velocities

Combining Velocities If the train is moving forward at 70 mph and the guy throws the ball forward at 20 mph, how fast does the ball move according to the guy on the ground? 90 mph!

Combining Velocities If you’re riding in a bus traveling east at 55 mph, you and all other passengers are also traveling at a velocity of 55 mph east. But suppose you stand up and walk down the bus’s aisle at 2 mph west. Are you still moving at the same velocity as the bus? NO! And the resultant velocity is 53 mph east!

Combining Velocities When you combine two velocities that are in the same direction – add them together to find resultant velocity! When you combine two velocities that in opposite directions – subtract the smaller velocity to find the resultant velocity. This velocity will be in the direction of the larger velocity!

Acceleration  Which is an example of acceleration? –Sally slowed down to a stop at the end of her bike ride –The light turned green so the car drove forward –Sally was so excited to arrive in science class, she turned the corner into Mrs. Chamberlain’s room without changing her speed

Acceleration DOES NOT = “to speed up” Acceleration = the rate at which velocity changes In other words…change of speed OR change of direction Acc = (final velocity – starting velocity)/time

Acceleration Positive acceleration = speed increases Negative or deceleration = speed decreases Change in direction = change in acceleration

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