How do you know when an object is moving?

MOTION

What is Motion?

Turn and Talk - See if you and your partner can come up with a definition.

What is Motion?

a change in position, relative to a frame of reference.

Reference Point

Movement

But wait…..

Before we talk about motion, lets talk about physical quantities in general.

There are two types of physical quantities:

SCALAR and VECTOR

What is a SCALAR QUANTITY?

Only needs the MAGNITUDE to describe it

The “HOW MUCH”A numerical value.

Examples: A cat has a mass of 5 kg

Johnny runs 100 meters in 10 seconds

What is a vector quantity?

Needs the MAGNITUDE and the DIRECTION

Which way?How Much?

Example: The cat runs 2.5 meters per second east as it chases the squirrel.

Example: The cat runs 2.2 meters per second east as it chases the mouse.

Back to how we study motion...

scalar vector

distance displacement

speed velocity

acceleration

ALL motion can be described with these 5 quantities.

X Axis

Y Axis

Distance = how far an object has moved.

Measured in meters, kilometers (cm or mm)

If each mark represents 10 cm, what is the distance between the girl and the ball?  ______

Displacement = Final Position - Initial Position

What if Sally walks to the red ball and then back to the teddy bear?

What is her distance?

What is her displacement?

X Axis

Y Axis

Objects to the right of 0 have a POSITIVE position

Objects to the left of 0 have a NEGATIVE position.

What is the position of the Smiley Face? ______________

Lightning Bolt _______________

Heart? ______________

Speed = the distance an object travels per unit of time  (sec, hour, year..etc)

Speed Equation

Speed (meters/second)  =  distance (in meters)                                                   time (sec)

                           S = d                           t

A car travels a distance of 500 m in 10 sec.  What is the car's speed?

  S = d         t

A second car travels a distance of 100 meters in 20 seconds.  What is this car's speed?  

More practice.  (Speed = distance/ time)

An elevator travels from the first floor to the 25th floor of a building, a distance of 180 meters, in 60 seconds. What is the elevator's speed?

Find the Distance = ______

Find the Time = _______

Calculate the Speed =  _______

What is Velocity?

Velocity is a measure of the speed of an object AND the direction it is moving in space.

On the escalator, passengers are moving at the same speed, but they are moving in different directions. 

So….. they have different

VELOCITIES  V = Δd         Δt

and include a direction

Speed is......._____________________________

Velocity is .... _____________________________

A car travels north 600 m in 10 sec.  What is the car's velocity?

  V = Δd         Δt

Your results should have:

NUMERICAL ANSWER

UNITS

DIRECTION

Average Velocity = total distance traveled                                      time taken

This is useful when you are trying to measure speed, and the object moved at varying speeds throughout the trip.  For instance, if you drove from here to Busan, you might AVERAGE 60km/h, even though you stopped at lights, or slowed down or travelled at 70 km/h at some points on your trip.

On graphs that show distance versus time, the SLOPE of the line is a measure of the velocity of the object.

Distance vs Time

1. Calculate each average velocity.

Bill ______

Myrtle ______

Zed ______

2.  Can you find from the graph, the point where Zed stopped for a while?

3.  Which turtle wins the race?

4.  At what time period was Bill and Myrtle's speed the same?

Constant Speed 

Constant speed means that the speed stays the same throughout the entire distance

*Very few things can stay at a constant speed.  Rather, things usually move at a constant speed for a period of time. 

The cyclist speeds up, slows down, stops..etc

Velocity = distance/time (more practice)

1.  If a person is walking at 4 m/s, how far can he travel in 30 seconds?

a)  120 meters       b)  7.8 meters       c) .08 meters

2.  A spaceship can move 100 meters in 2 seconds.  What is the ship's velocity?

a)  200 m/s              b)  50 m/s            c)  .002  m/s

3.  A chicken runs across the street at a speed of 12 m/s.  If the road is 36 meters across, how long does it take for the chicken to cross the road?

a)  3 s         b)  432 s          c)  .333 s

QUIZ TIME -  MOTION

1. Motion indicates a change in _____________

2.  Motion is relative to a ___________ of reference.

3. Write the equation for displacement: _______

4. Write the equation for velocity:

5. What units (standard) are used for velocity? ___

6. What units are used for distance? ____

7. Vector quantities measure magnitude and ___.

 

8. How far did the object move at 6 seconds? ______

9. If Y2 = 5 Y1 = 0

Calculate the slope.

10. The slope of the line is a measure of the object’s? ____

Acceleration = the rate of change of velocity

Change in Velocity =                  final velocity (vf) - initial velocity (vi)

Acceleration (m/s2) =   (vf) - (vi)                                      time

units

Change in velocity is often written as 

the triangle indicates "change"

acceleration = change in velocity                       change in time

If a car moves at a constant velocity, then its acceleration is zero

Calculations

A skateboarder is traveling at 8 m/s.  He slows and comes to a stop in 4 sec.  What was the acceleration?  (hint: it is a negative number)

What is the v (final v)?  _____

What is the u (initial v)? _____

What is the acceleration? _______

A sailboat is moving at 12 m/s when a gust of wind changes its velocity to 18 m/s.  The wind lasts 10 seconds.  For that 10 sec, what was its acceleration?

What is the v (final v)?  _____

What is the u (initial v)? _____

What is the t?  _______

Acceleration? ________

Positive acceleration = speeding up

Negative acceleration (aka deceleration or retardation) = slowing down

A Ducati can accelerate to 97 km/h

in 3 seconds.

A Ducati can accelerate to 97 km/h or 27 m/s in 3 seconds.

What is the acceleration of a Ducati if it starts at 0 and gets to a velocity of 27 m/s in 3 sec?

So consider this situation….. a coppulls you over forspeeding:The distance between the stop sign and the school parking lotentrance is 40 meters.

The cop says your velocity was 20 m/s.

How long would it take you (t) to travel a distance of 40 meters at that speed?

  V = d         Δt

So, putting all the data together, according to the cop

Your initial velocity (at stop sign) was 0 m/s

Your final velocity (at entrance) was 20 m/s

The time it took you to travel that distance would be 2 sec.

What would have been your acceleration?

Is this faster or slower than the ducati?

Think about this....

   What are three ways to change the velocity of a car?

Accelerate

Decelerate

Change direction

Graphs represent speeds of objects.  This graph shows a bus as it travels its

route.  

Between what points is the bus accelerating? _____  &  ____Between what points is the bus moving at a constant speed?                                                               _____  &  _____Between what points is the bus stopped?  __________Between what points it the bus decelerating? _________

QUIZ TIME -  MOTION

1.  The triangle in the equation represents ________

2. If you are slowing down, then you have a ____________acceleration.

3. A bike that goes from 6 m/s to 16 m/s in 20 seconds. Set up the equation that you would use to calculate the acceleration of the bike.

4. Solve the equation in #3.

5. What units are used for acceleration?

5. The bike changes its velocity again, going from 16 m/s to a stop over a period of 8 seconds.

Set up the equation.

6. What is its acceleration? Make sure to include + or -

How can you measure the velocity of a mealworm?