1. Chapter 2 Section 1 Describing Motion

2. When I think of Motion I think of movement and SPEED!
Fast Cars or Trucks
OR Even Fast People

3. But exactly how do we determine if something is moving?

4. By using a Reference Point
A stationary object in the background that is not going to move.
We compare the position of the non moving object to that of something that we think is moving.
Examples ?

5. And now I can define Motion
Motion is a change in an object’s position relative to a reference point.

6. Creating a frame of Reference to measure distance
Frame of reference is a coordinate system in which the position of the object can be measured.
Coordinate System is like a map. The reference point is at the origin (start), and each object’s position can be described with coordinates x and y.

7. Distance vs Displacement
Displacement is the shortest distance from the initial to the final position. Thus, it is the length of an imaginary straight path, typically distinct from the path actually travelled.
Initial
Final

8. Displacement is As the Crow Flies
Who is the Crow, Alan or Eva? What is both of their displacements?

9. What is the displacement of a track star who travels 400m around the track?
Blue man is heading home and travels a path of A to B to C. What is his distance traveled? What is his displacement?

10. SPEED!
Speed is the distance traveled divided by the time it took to travel that distance.
Formula - Speed = distance/time
So in order to measure speed I have to have Distance (km, m) and Time (hr, s)
Units (derived units) mi/hr, km/hr, m/s

11. Usain Bolt Breaks Olympic Record
If Usain Bolt can run 9.58 seconds in 100 meters what is his speed?
Data Formula Work Ans
S= s=d
d= t t=

12. Another Speed Problem
A car traveling at a constant speed (traveling equal distance in an equal amount of time) covers a distance of 750 m in 25 s. What is the car’s speed?
Data Formula Work Ans
Work Problems 1-4

13. Speed can also be calculated by looking at a distance-time graph
Calculate the bikers Instantaneous Speed at B (speed at a given instant-like using a speedometer in a car)

14. Reading Distance/Time Graphs Speed Graphs

16. Section 2 Velocity and Momentum

17. What is Velocity?
A quantity describing both speed and direction. Speed in a given direction.
20 m/s North, or 95 mi/hr towards home plate
Formula is the same as speed plus direction.
Velocity of the object can change even if the speed remains constant, how?

18. Velocity Problem
What is the velocity of a swimmer who swims exactly 110 m toward the shore in 72 s?
Data Formula Work Ans

19. Motion of the earth’s crust
Plates move along the San Andreas Fault in California at 1 cm/y
Australian Plates move at 17 cm/y pushing Australia North at a velocity of 17 cm/y North

20. Relative Motion
A person sitting in a seat on a moving train is a rest relative to the train, but the person is moving relative to the ground.
All depends on your reference point
What are some other situations where you are moving relative to one object and at rest relative to another?

21. Momentum Momentum is a commonly used term in sports.
A team that has the momentum is on the move and is going to take some effort to stop.
Momentum is a physics term; it refers to the quantity of motion that an object has. A sports team that is on the move has the momentum. If an object is in motion (on the move) then it has momentum.

22. Momentum- Physics Momentum can be defined as "mass in motion."
All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion.
Momentum is dependent upon two variables: Mass and Velocity.
Formula Momentum = mass x velocity
Units Mass(kg) x Velocity (m/s) = kg x m/s
p = m x v Draw Triangle

23. Momentum Problem
A car moving 20 m/s has a mass of 2000 kg, what is the car’s momentum? Data Formula Work Ans Work Momentum problems

24. Section 3 Acceleration

25. Acceleration
When you gain speed or slow in a car, your velocity changes.
Velocity also changes when you turn or change directions. (velocity is speed plus direction)
Any change in velocity is acceleration.
Positive acceleration = speed up
Negative acceleration = slowing down

26. Finding Acceleration You need velocity at different times
Accel= final velocity - initial velocity
time
Or a= v t
v = final velocity - initial velocity
Units for acceleration = m/s2, meters per second squared

27. Acceleration Math
A flower pot falls off a second story windowsill. The flower pot starts from rest and hits the sidewalk 1.5 s later with a velocity of 14.7 m/s. Find the acceleration of the flower pot. Data Formula Work Ans vf= a = vf - vi vi= t t=

28. More Math
What is the average acceleration of a car that starts from rest and moves straight ahead at 18 m/s in 12 s ? Data Formula Work Ans vf= a = vf - vi vi= t t=

29. Graphs
Speed graphs are _______ - ________ graphs. Acceleration graphs are _______-______ graphs.
Distance
Time
Velocity
Time

30. Acceleration Graphs
Draw graph and identify acceleration, deceleration, and no acceleration

31. Motion in 2 Dimensions
Circular motion – a horse on a carousel, its speed remain constant but it is accelerating because its direction is changing.
Centripetal Acceleration – acceleration toward the center of a curved or circular path.

32. Motion in 2 Dimension
Projectile motion – throwing a ball to someone, curved downward path
The object has horizontal acceleration, then gravity causes it to accelerate downward