Physics 151 Week 2 Day 3
Topics
– Motion Diagrams & Motion Graphs
– Motion Definitions
– Velocity to position
Two Ships Passing in the Night
Ships P and Q move with the
position graphs shown. Both
ships are at the origin at t = 0s.
When does one pass the other?
A.
B.
C.
D.
at t = 2 s.
at t = 1 s and at t = 3 s.
at t = 1 s, 2 s, and 3 s.
P and Q never pass one another.
Slide 2-34
Two Ships Passing in the Night
Ships P and Q move with the
position graphs shown. Both
ships are at the origin at t = 0s.
When does one pass the other?
A.
B.
C.
D.
at t = 1 s and at t = 3 s.
Slide 2-34
Two Ships Passing in the Night
Ships P and Q move with the
position graphs shown. Both
ships are at the origin at t = 0s.
Do P and Q ever have the same
velocity? If so, at what time or
times?
A.
B.
C.
D.
P and Q have the same velocity at 2 s.
P and Q have the same velocity at 1 s and 3 s.
P and Q have the same velocity at 1 s, 2 s, and 3 s.
P and Q never have the same velocity.
Slide 2-34
Answer
Ships P and Q move with the
position graphs shown. Both
ships are at the origin at t = 0s.
Do P and Q ever have the same
velocity? If so, at what time or
times?
A.
P and Q have the same velocity at 2 s.
Slide 2-35
Motion Diagrams
Representations of Motion
Motion diagram (student walking to school)
Table of data
Graph
Slide 2-9
Checking Understanding
Here is a motion diagram of a car moving along a straight stretch
of road:
Which of the following velocity-versus-time graphs matches this
motion diagram?
A.
B.
C.
D.
Slide 2-13
Answer
Here is a motion diagram of a car moving along a straight stretch
of road:
Which of the following velocity-versus-time graphs matches this
motion diagram?
C.
Slide 2-14
Checking Understanding
A graph of position versus time for a
basketball player moving down the
court appears like so:
Which of the following velocity graphs matches the above
position graph?
A.
B.
C.
D.
Slide 2-15
Answer
A graph of position versus time for a
basketball player moving down the
court appears like so:
Which of the following velocity graphs matches the above
position graph?
C.
Slide 2-16
Can you move?
Fill in the tables for these motion events by indicating whether or not a
motion event is possible. If it is, give an example. If not, explain why not.
Displacement
0
0
Not 0
Not 0
Final Position
0
Not 0
0
Not 0
Possible?
Example/Explanation
Average Speed
Average
Velocity
0
Not 0
0
Not 0
Possible?
Example/Explanation
0
0
Not 0
Not 0
Slide 1-7
There and Back
You and a friend decide to drive to Las Vegas, Nevada on
Saturday over Labor Day weekend to go to a concert with some
friends who live there. You figure you have to reach the vicinity
of Las Vegas by 6 PM in order to meet your friends for dinner
before the concert.
1. It's 574 miles from UNM to the Las Vegas strip. You'd like
to stop for lunch and gas bout noon. What does your
average velocity need to be?
2. It's almost all highway driving from here to Las Vegas. If
you keep your speed approximately constant, what speed
should your speedometer read while you are driving?
3. After you return to UNM, what is your displacement from
the time you left to go to Las Vegas? What is the total
distance traveled? What is your average speed and
velocity?
Slide 1-7
Where’s the train?
A train is moving at a steady 30 m/s. At t = 0, the engine
passes a signal light at x = 0. Without using any formulas,
find the engine's position at t = 1s, 2s, and 3s.
Express your reasoning in words.
Slide 2-34
Velocity to Position: Example 1
Find the position at times t = 1, 2, 3, 4, and 5 seconds.
Assume x (t = 0 sec) = 0 m.
What is the displacement of the object between t = 1s and t =
3 s?
Slide 2-34
Velocity to Position: Example 2
• Describe in words the motion of the object whose velocity
graph is given below. What is happening at t = 2 s?
• Draw a motion diagram of the objects motion.
• Draw the corresponding position vs. time graph.
Assume initial position is 5 m.
• Give an example of an object that would move this way
Slide 2-34
Acceleration
Acceleration is:
•
The rate of change of
velocity
•
The slope of a velocityversus-time graph
Slide 2-20
Reading Quiz
3. If Sam walks 100 m to the right, then 200 m to the left, his net
displacement vector points
A. to the right.
B. to the left.
C. has zero length.
D. Cannot tell without more information.
Slide 1-6
Answer
3. If Sam walks 100 m to the right, then 200 m to the left, his net
displacement vector points
B. to the left.
Slide 1-7
Reading Quiz
4. Velocity vectors point
A. in the same direction as displacement vectors.
B. in the opposite direction as displacement vectors.
C. perpendicular to displacement vectors.
D. in the same direction as acceleration vectors.
E. Velocity is not represented by a vector.
Slide 1-8
Answer
4. Velocity vectors point
A. in the same direction as displacement vectors.
Slide 1-9