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?

Matter in MotionMatter in Motion

Chapter 1.1Chapter 1.1

pp. 4-10pp. 4-10

MotionMotionHow do we know something is How do we know something is moving?moving?

Is this guy in motion? How do you Is this guy in motion? How do you know?know?

Measuring MotionMeasuring Motion

Must observe motion in relation to Must observe motion in relation to another objectanother object

Reference Point = an object that Reference Point = an object that appears to stay in place in relation to appears to stay in place in relation to an object being observed for motionan object being observed for motion

(earth surface, tree, etc.)(earth surface, tree, etc.)

MotionMotion

Motion = object changing position Motion = object changing position over time when compared to a over time when compared to a reference pointreference point

Two elements: position and timeTwo elements: position and time

SpeedSpeed

How do we know an object’s speed?How do we know an object’s speed?

It depends on two factors: It depends on two factors:

distance and timedistance and time

Speed = rate at which an object Speed = rate at which an object movesmoves

Ave speed = total distance/total timeAve speed = total distance/total time

Speed on a graphSpeed on a graph

VelocityVelocity

What if I said “Johnny left CCMS and What if I said “Johnny left CCMS and walked 1 mile” Can you know where walked 1 mile” Can you know where he ended up? Why or why not?he ended up? Why or why not?

Velocity = speed of an object Velocity = speed of an object in a in a particular directionparticular direction

Changes when SPEED or DIRECTION Changes when SPEED or DIRECTION changeschanges

Sometimes can combine velocitiesSometimes can combine velocities

Combining VelocitiesCombining VelocitiesIf the train is moving If the train is moving forwardforward at 70 at 70 mph and the guy throws the ball mph and the guy throws the ball forwardforward at 20 mph, how fast does the at 20 mph, how fast does the ball move according to the guy on ball move according to the guy on the ground? the ground?

90 mph!90 mph!

Combining VelocitiesCombining VelocitiesIf you’re riding in a bus traveling east at 55 mph, you and 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 all other passengers are also traveling at a velocity of 55 mph east.mph east.

But suppose you stand up and walk down the bus’s aisle at 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 2 mph west. Are you still moving at the same velocity as the bus? the bus?

NO! And the resultant velocity is 53 mph east!NO! And the resultant velocity is 53 mph east!

Combining VelocitiesCombining Velocities

When you combine two velocities that When you combine two velocities that are in the are in the same directionsame direction – add them – add them together to find resultant velocity!together to find resultant velocity!

When you combine two velocities that When you combine two velocities that in in opposite directionsopposite directions – subtract the – subtract the smaller velocity to find the resultant smaller velocity to find the resultant velocity. This velocity will be in the velocity. This velocity will be in the direction of the larger velocity!direction of the larger velocity!

AccelerationAcceleration Which is an example of Which is an example of

acceleration?acceleration?– Sally slowed down to a stop at the end Sally slowed down to a stop at the end

of her bike rideof her bike ride– The light turned green so the car drove The light turned green so the car drove

forwardforward– Sally was so excited to arrive in Sally was so excited to arrive in

science class, she turned the corner science class, she turned the corner into Mrs. Chamberlain’s room without into Mrs. Chamberlain’s room without changing her speedchanging her speed

AccelerationAcceleration

DOES NOT = “to speed up”DOES NOT = “to speed up”

Acceleration = the rate at which Acceleration = the rate at which velocity changesvelocity changes

In other words…change of speed OR In other words…change of speed OR change of directionchange of direction

Acc = (final velocity – starting Acc = (final velocity – starting velocity)/timevelocity)/time

AccelerationAccelerationPositive acceleration = speed Positive acceleration = speed increasesincreases

Negative or deceleration = speed Negative or deceleration = speed decreasesdecreases

Change in direction = change in Change in direction = change in accelerationacceleration