7th Grade-Chapter 1 Motion Powerpoint Notes

Describing and Measuring Motion How do you recognize motion?  An

object is in motion when its distance from another object is changing  Movement depends on your point of view

What is a reference point? A

place or object used for comparison to determine if something is in motion

 An

object is in motion if it changes position relative to a reference point

Determining When an Object is in Motion or not an object is in motion depends depends on  on the reference point you choose & if the distance between  the object and the reference point is changing.

 Whether

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SWBAT: Investigate, measure and describe what happens to the motion, speed ,velocity and acceleration of moving objects

Negative Distance & Football 

Question: Can a distance be negative in relationship to a reference point?

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point in football Football Example: Reference point in (below), positive (below),  positive play (right), play (right), negative playsacked for a loss (bottom loss (bottom right)

Which of the following is true if you are riding your bike past the middle school? A. You are are moving moving rel relativ ativee to the the bike, bike, but not not the scho school. ol. B. You are not mov moving ing rel relativ ativee to the sch school ool or the the bike. bike. C. You are are moving moving rel relativ ativee to the the school school,, but not not relativ relativee to the the bike. D. You are are moving moving rel relativ ativee to the the bike bike and the the school school..

What is the basic unit of length?  The

meter  a little longer than a yard –

What do scientists use to measure the length of an object smaller than a yard? A

centimeter  one hundredth of a meter, so there are 100 centimeters in a meter  A millimeter  There are 1,000 millimeters in a meter –

–

How do scientists measure long distances?  The

kilometer  There are 1,000 meters in a kilometer –

  1mile=

1.6km

How do scientists calculate speed? 

Speed  the distance the object travels in one unit of time  Rate  tells you the amount of something that occurs or changes in one unit of time  Speed = distance time –

–

What is constant speed?  If

the speed of an object does not change, the object is traveling at a constant speed

What is average speed?  Most

objects do not move at constant speeds for very long

 To

find average speed divide the total distance by the total time Car trip

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Calculating Speed 

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How can you calculate speed? If you travel 45 km in 3 hours, what is your average speed? 

Speed = change in distance/change in time

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Instant speed is speed is your speed at a certain time.

 Average speed is speed is your averaged speed for the ENTIRE trial, event, or race. 

Avg. speed = change in distance/change in time

What is Velocity?  Speed in

a given direction

 When

you know the speed and direction of an object s motion, you know the velocity of the object ’

 Example

15 km/hour westward

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Do Now: What is the speed sp eed average speed of a car that traveled 75km/h in 5 hours

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Speed= Distance/ Time

Distance= 75km , Time =5 hours so 75km/5hrs= 15km/hr 

SWBAT: Investigate, measure and describe what happens to the motion, speed ,velocity and acceleration of moving objects

How do you graph motion?  You

can show the motion of an object on a line graph in which  you plot distance against time

 Time is

along the xaxis and distance on the y-axis

How do you interpret motion graphs? A

straight line indicates a constant speed

 The

steepness depends on how quickly or slowly the object is moving  The faster the motion the steeper the slope

Distance Determination (from a Speed-Time Graph)

SPEED (m/s)

5 m/s 1s

2s

Time (s) 

How far will the object have gone in 2 seconds? 

10 meters (5 m/s x 2 s)

Or 

Determine the area area under the line: Create a rectangle rectangle and determine its area (l x w = 2 s x 5 m/s = 10 m) 

SWBAT: Investigate, measure and describe what happens to the motion, speed ,velocity and acceleration of moving objects

Graphing Motion (Calculating speed)  You

can show the motion of an object on a line graph in which you plot distance versus time. time. Remember: Velocity is the change in distance in a certain direction during a certain length of time. So, velocity or speed = rise/run

Speed vs. Velocity 

Do Now: Mark is jogging at 6.0 mph, while Sue is also jogging at 6.0 mph. However, Mark s velocity is -6.0 mph while Sue s is 6.0 mph. Why are their speeds the same, but their velocities are different? ’

’

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SWBAT: Investigate, measure and describe what happens to the motion, speed ,velocity and acceleration of moving objects

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Goal: Determine the difference between SPEED and VELOCITY.

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you think is the difference between speed and velocity? Hypothesis: What do you

Speed vs. Velocity Experiment Were there any negative velocities? velocities? Why is this this the case? Is velocity  just speed? If not, what else is is factored in to velocity? Hint- Think about when your velocity was negative relative to the motion sensor, and keep in mind that speed is NEVER negative. •

Scenario:

Mark is jogging at a speed of 6.0 mph, mph, while Sue is also  jogging at a speed of 6.0 mph. However, Mark ’s velocity is -6.0 mph while Sue’s is 6.0 6.0 mph. Why are their speeds the same, but but their velocities are different?

Velocity

So,

= speed + direction relative to a reference point

Mark was going just going just as fast as fast as Sue, but in the opposite direction.

Peregrine Falcons  can  can dive at speeds up to 242 mph.

 The

What is Acceleration?

rate at which velocity changes  In science, acceleration refers to:  increasing speed  decreasing  speed  changing direction

How do you calculate acceleration?  To

determine the acceleration rate of an object, you must calculate the change in velocity during each unit of time

 Acceleration

= Final velocity – Starting velocity Time

Calculating Acceleration 

What does it mean if a car accelerates? Have you ever heard of of a car that can go go 0 to 60 mph in mph in about 6 seconds? seconds? (Just like mine). What about when a car decelerates?

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To determine the acceleration of an object moving in a straight line, you must calculate the change in velocity per unit of time t ime 

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Average Acceleration = (final velocity – starting velocity)/time

Acceleration- The rate at which velocity changes

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Graphing You can Acceleration use both a speed-versusa speed-versus-time time graph and a distance-versus-time distance-versus-time graph  graph to analyze the motion of an accelerating object.

Calculating Acceleration 

As a roller-coaster car starts down a slope, its speed is 4 m/s. But 3 seconds later, at the bottom, its speed is 22 m/s. What is its average acceleration?

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Read and Understand

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What information have you been given?

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Initial speed = 4 m/s

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Final Speed = 22 m/s

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Time = 3 s

Calculating Acceleration 

As a roller-coaster car starts down a slope, its speed is 4 m/s. But 3 seconds later, at the bottom, its speed is 22 m/s. What is its average acceleration?

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Plan and Solve

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What quantity are you trying to calculate?

 

  

The average acceleration of the roller-coaster car = __ What formula contains the given quantities and the unknown quantity? Acceleration = (Final (Final speed  –  Initial speed)/ speed)/Time Time Perform the calculation. Acceleration = (22 (22 m/s  –  4 m/s)/ m/s)/3 3 s = s = 18 m/s/3 m/s/3 s

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Acceleration = 6 m/s2

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The roller-coaster car  s average acceleration is 6 m/s2.

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This is a positive acceleration (speeding up).

’

Calculating Acceleration 

As a roller-coaster car starts down a slope, its speed is 4 m/s. But 3 seconds later, at the bottom, its speed is 22 m/s. What is its average acceleration?

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Look Back and Check 

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Does your answer make sense?

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The answer is reasonable. If the car  s speed increases by 6 m/s each second, its speed will be 10 m/s after 1 second, 16 m/s after 2 seconds, and 22 m/s after 3 seconds. ’

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Calculating Acceleration 

Practice Problem



A certain car brakes from 27 m/s to rest in 9 seconds. Find the car  s average acceleration. ’

÷ 9

s = -27 m/s ÷ 9 s = -3 m/s2

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(0 m/s  –  27  27 m/s )

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This is a negative acceleration, acceleration, which is also called a deceleration (slowing down)