1. Motion Objectives: Displacement, velocity, acceleration
Motion with Constant Acceleration
Free Fall

2. Distance and Displacement
Q1. The width of a room is 7 m (approx. 7 yards). You walk from one wall to the other wall, what is the total:
Distance
Displacement

3. Distance and Displacement
Q1. The width of a room is 7 m (approx. 7 yards). You walk from one wall to the other wall, what is the total:
Distance: 7 m
Displacement: 7 m
Q2. Now, you walk back to the wall where you started originally. What is the total:
Distance:
Displacement:

4. Distance and Displacement
The length of the path traveled
Displacement
The CHANGE in the position

5. Distance and Displacement
The length of the path traveled
Displacement
The CHANGE in the position
Q3. You dive in the swimming pool and begin to do laps. The swimming pool is 25 m long. After 2 complete laps, what is the distance traveled?
(a) 0
(b) 50
(c) 100
(d) Cannot tell

6. Distance and Displacement
The length of the path traveled
Displacement
The CHANGE in the position
Q3. You dive in the swimming pool and begin to do laps. The swimming pool is 25 m long. After 2 complete laps, what is the distance traveled?
(a) 0
(b) 50
(c) 100
(d) Cannot tell
Q4. What is your total displacement?
(a) 0
(b) 50
(c) 100
(d) Cannot tell

7. Velocity and Speed displacement distance traveled = time it took speed
change in position =
time it took
velocity
number
number +
direction

8. Velocity and Speed Speed or velocity? displacement distance traveled =
time it took
speed
change in position =
time it took
velocity
number
number +
direction
Speed or velocity?
You are driving your car at 65 mph.
You are lost and call a friend to tell him you are driving north at 45 mph
You tune in to the Weather channel and they report north-west winds at 50 mph

9. Velocity and Speed
displacement
distance traveled =
time it took
speed
change in position =
time it took
velocity
number
number +
direction
Q5. The width of a room is 7 m (approx. 7 yards). You walk from one wall to the other wall and back in 10 s. What was your speed?
And your velocity?

10. Velocity and Speed
displacement
distance traveled =
time it took
speed
change in position =
time it took
velocity
number
number +
direction
Q5. The width of a room is 7 m (approx. 7 yards). You walk from one wall to the other wall and back in 10 s. What was your speed?
And your velocity?
distance traveled =
time it took
speed
displacement =
time it took
velocity
speed = ?
velocity = ?

11. Acceleration displacement average distance traveled = time it took
speed
average
change in position =
time it took
velocity
average
change in velocity =
time it took
acceleration

12. Acceleration
displacement
average
distance traveled =
time it took
speed
average
change in position =
time it took
velocity
average
change in velocity =
time it took
acceleration
Q6. Claims on the web state that a NASCAR Cup car can run 0 – 60 in 3.0 s. What is its average acceleration? ?
average
change in velocity =
time it took
acceleration
Ans. ?

13. Displacement, Velocity, Acceleration20
P1. Your speedometer reads 50 mph. Is this average speed or instantaneous?
Answer:
P2. You are driving at 35 mph. What Is that in m/s?
Answer:
P3. A car accelerates from 60 ft/s to 70 ft/s. What Is its average acceleration? What is the acceleration in m/s?
Answer:
P4. A pick up truck pulling a trailer accelerates at 3.25 m/s2 for 5.80 s. If it starts from rest, what is its final velocity?
Answer:

14. Average vs. Instantaneous
Q7. How can we calculate the speed or velocity at one instant?
acceleration =
constant
velocity =
Beginning velocity +
acceleration x
time elapsed
position =
beginning position
We’ll simplify this and use it for free fall. +
beginning velocity x
time elapsed 2 +
0.5 acceleration x
time elapsed

15. Free Fall Q8. Which one will hit the ground first? (a) Ball (b) Paper
(c) Both
(d) Cannot tell
Class demo . Do paper and ball. Clicker question to see what they think.

16. Free Fall Galileo (1589): 186 ft 1 s: 16 ft 2 s: 64 ft 3 s: 144 ft
Galileo’s Experiment

17. Free Fall Galileo (1589): 186 ft Pattern 1 s: 16 ft 1 2 s: 64 ft 4
Galileo’s Experiment : The Pattern of distance ~ (t)^2
4 s:
?? ft ??

18. Free Fall Apollo 15 Moon Experiment: Pattern 1 s: 16 ft 1 2 s: 64 ft 49
144 ft
Apollo 15 Experiment on the Moon
Apollo 15 Moon Experment with a Hammer and a Feather

19. Free Fall: Example
Q9. The acceleration due to Earth’s Gravity is 9.8 m/s2. What is that in ft/s2?
Answer:
Fill in the numbers and calculate

20. Free Fall: Example
10 min
Q10. If you drop a rock from the top of a building and it hits the ground 1.5 s later, how tall is the building in ft?
acceleration =
ft /s2
velocity =
Beginning velocity +
ft /s2 x
time elapsed
Fill in the numbers and calculate
position =
beginning position +
beginning velocity x
time elapsed 2 +
(0.5) ft /s2 x
time elapsed

21. Free Fall Problems
DIY
P1. Your speedometer reads 50 mph. Is this average speed or instantaneous?
Answer:
P2. You are driving at 35 mph. What Is that in m/s?
Answer:
P3. A car accelerates from 60 ft/s to 70 ft/s. What Is its average acceleration? What is the acceleration in m/s?
Answer:
P4. A pick up truck pulling a trailer accelerates at 3.25 m/s2 for 5.80 s. If it starts from rest, what is its final velocity?
Answer:

22. Constant Acceleration Problems
DIY
P1. You drop a rock from a bridge. It hits the water in 3.0 s. How far below is the surface of the water?
Answer: =
position +
(0.5) ft /s2 2 x
Fill in the numbers and calculate
P2. What will be the speed of a rock 1.5 seconds after it has been dropped?
Answer: =
velocity + x
ft /s2