1. Motion Chapter 11

2. What is physics? The study of matter and energy and…
The interactions between the two…
Through forces and motion
Topics in physics
Motion, forces, work, power,
machines, energy, waves, heat,
light, sound, optics, electricity,
magnetism and more…

3. Frame of Reference
Motion of an object in relation to a fixed body or place.
To describe motion accurately and completely
THE MOST COMMON FRAME OF REFERENCE: The Earth

4. Relative Motion Is the movement in relation to a frame of reference
Example:
A train going past a platform (see movement)
People riding the train feel
no movement

5. Distance Length of a path between two points How far, long, wide, etc
Metric units for distance – meter, kilometer, centimeter, etc.
Units should match the distance – longer units for longer distances, shorter units for shorter distances

6. Measuring Displacement
the direction from the starting point and the length of a straight line from the starting point to the ending point
Involves distance and direction

7. Combining Displacement
Vector—is a quantity that has magnitude and direction
Add displacements using vector addition
If vectors are in the same directions, add them
Ex:
10 meters meters = meters
If vectors are in the opposite direction, subtract them
20 meters meters = 5 meters
Resultant vector—the vector sum of two or more vectors

8. Steps in solving word problems 1. READ the problem carefully. 2
Steps in solving word problems 1. READ the problem carefully. 2. Choose the correct FORMULA and write it down. 3. Identify INFORMATION given in the problem. Determine the VARIABLE, what you are looking for 4. Substitute the known INFORMATION into the formula. 5. SOLVE the equation for the variable. 6. Give the answer including NUMBER and appropriate UNITS.

9. v Speed Rate of Motion: Change of position in a given amount of time.
Formula:
Speed = Distance/time
Units: km/h, m/s
v = speed v = average speed
d = distance t = time d
v = t v
vvv
Delta T diagram

10. Speed Average Speed Is computed for the entire duration of a trip
Instantaneous Speed
Is the rate at which an object is moving at a given moment of time
Speed right now

11. Speed Practice Problems
How long does it take a bird to fly 300km if it travels at a speed of 50 km/h?

12. 2. Alex rode his bicycle 60 kilometers in 4 hours
2. Alex rode his bicycle 60 kilometers in 4 hours. How fast was he going?

13. 3. Joe can pitch a baseball 32 m/s and the ball crosses the plate in 1
3. Joe can pitch a baseball 32 m/s and the ball crosses the plate in 1.5 seconds. How far away is the plate?

14. 4. Kayla runs 90 meters with a speed of 15 m/s. How long did it take?

15. Velocity Velocity= Speed in a given direction. Velocity is a vector
You combine velocities the same way you combine displacement
Same direction, add them
Opposite direction, subtract them

16. Velocity
Formula
V=Δd/Δt
V=velocity
d=distance
t=time
Units: m/s

17. Graphs of Speed and Velocity
Constant Speed
Not Moving
Constant speed and then not moving

18. Acceleration Rate of change in velocity. Acceleration is a vector
Formula: a = vf – vi or Δv
t t
Unit: m/s2
Variables need to solve acceleration problems
2 Velocities
Time

19. Deceleration Negative Acceleration
Solve it just like the acceleration problem but the answer is always
NEGATIVE
Tom sees a stop sign. He notices his speedometer is on 50 km/h, applies the brakes, and comes to a full stop in 10 seconds. What is his average acceleration in km/h/s?
a = vf – vi or Δv
t t
a = ? vf = 0 km/h vi = 50 km/h t = 10 s
a = 0 km/h – 50 km/h
10 s
= -50 km/h = -5 km/h/s
10 s

20. Acceleration/ Deceleration Problems
A car starts from rest and goes to 20 m/s in 4 seconds. What is the car’s acceleration?

21. 2. A runner starts to run and reaches a velocity of 100 m/s in 25 seconds? What is the car’s acceleration?

22. 3. A train slows down from 200 m/s to a stop in 50 seconds
3. A train slows down from 200 m/s to a stop in 50 seconds. What is the car’s deceleration?

23. 4. A train has an acceleration of 40 m/s2 during a period of 15 seconds. What is the train’s velocity?

24. Graphs of Acceleration
Deceleration
Constant Acceleration

25. Centripetal Forces Center Seeking
Centripetal Force is a force that pulls an object towards the center.
Center Seeking

26. Constant Speed and Circular Motion
An object moving in a circular motion may have constant Speed even though it is accelerating.
Why?

27. Answer: That object needs to change direction.

28. 3 ways objects accelerate
Change in Speed only
Change in Direction only
Change in Speed and Direction