Module 2, Recitation 2
Concept questions on v-t graphs
ConcepTest
Graphing Velocity I
1) it speeds up all the time
The graph of position versus
2) it slows down all the time
time for a car is given
3) it moves at constant velocity
below. What can you say
4) sometimes it speeds up and
about the velocity of the
sometimes it slows down
car over time?
5) not really sure
x
t
ConcepTest
Graphing Velocity I
The graph of position versus
time for a car is given
2) it slows down all the time
3) it moves at constant velocity
below. What can you say
about the velocity of the
car over time?
1) it speeds up all the time
4) sometimes it speeds up and
sometimes it slows down
5) not really sure
x
The car moves at a constant velocity
because the x vs. t plot shows a straight
line. The slope of a straight line is
constant. Remember that the slope of x
versus t is the velocity!
t
ConcepTest
The graph of position vs.
time for a car is given
below. What can you say
about the velocity of the
car over time?
Graphing Velocity II
1) it speeds up all the time
2) it slows down all the time
3) it moves at constant velocity
4) sometimes it speeds up and
sometimes it slows down
5) not really sure
x
t
ConcepTest
The graph of position vs.
time for a car is given
below. What can you say
about the velocity of the
car over time?
Graphing Velocity II
1) it speeds up all the time
2) it slows down all the time
3) it moves at constant velocity
4) sometimes it speeds up and
sometimes it slows down
5) not really sure
The car slows down all the time
because the slope of the x vs. t graph is
diminishing as time goes on.
Remember that the slope of x vs. t is
the velocity! At large t, the value of the
position x does not change, indicating
that the car must be at rest.
x
t
ConcepTest
v versus t graphs I
1) decreases
Consider the v versus t plot.
2) increases
How does the speed change
3) stays constant
with time?
4) increases, then decreases
5) decreases, then increases
v
t
ConcepTest
v versus t graphs I
1) decreases
Consider the v versus t plot.
2) increases
How does the speed change
3) stays constant
with time?
4) increases, then decreases
5) decreases, then increases
v
t
The initial velocity is positive
and the magnitude of the
velocity continues to increase
with time.
ConcepTest
v versus t graphs II
1) decreases
Consider the v versus t plot.
2) increases
How does the speed change
3) stays constant
with time?
4) increases, then decreases
5) decreases, then increases
v
t
ConcepTest
v versus t graphs II
1) decreases
Consider the v versus t plot.
2) increases
How does the speed change
3) stays constant
with time?
4) increases, then decreases
5) decreases, then increases
v
t
The initial velocity is positive but the
magnitude of the velocity decreases
toward zero. After this, the magnitude
increases again, but becomes negative,
indicating that the object has changed
direction.
ConcepTest
v
1
Rubber
v
3
t
v
2
t
You drop a rubber ball. Right after it
leaves your hand and before it hits the
floor, which of the above plots represents
the v vs. t graph for this motion?
(Assume your y-axis is pointing up).
Balls I
t
4
v
t
ConcepTest
v
1
Rubber
v
3
t
v
2
You drop a rubber ball. Right
after it leaves your hand and
before it hits the floor, which
of the above plots represents
the v vs. t graph for this
motion?
(Assume your y-
axis is pointing up).
t
Balls I
t
v
4
t
The ball is dropped from rest, so its
initial velocity is zero. Since the y-axis
is pointing upwards and the ball is
falling downwards, its velocity is
negative and becomes more and more
negative as it accelerates downward.
v
ConcepTest
1
vRubber Balls II
3
t
v
2
v
4
t
You toss a ball straight up in the air and
catch it again. Right after it leaves your
hand and before you catch it, which of
the above plots represents the v vs. t
graph for this motion? (Assume your yaxis is pointing up).
t
t
v
ConcepTest
1
vRubber Balls II
3
t
v
2
You toss a ball straight up in
the air and catch it again.
t
v
4
t
The ball has an initial velocity that is
Right after it leaves your hand
positive but diminishing as it slows. It
and before you catch it, which
stops at the top (v = 0), and then its
of the above plots represents
the v vs. t graph for this
motion? (Assume your y-axis
is pointing up).
t
velocity becomes negative and becomes
more and more negative as it
accelerates downward.
v
ConcepTest
1
Rubber Balls III
v
3
t
v
2
t
You drop a very bouncy rubber ball.
It falls, and then it hits the floor
and bounces right back up to you.
Which of the following represents
the v vs. t graph for this motion?
t
4
v
t
v
ConcepTest
1
Rubber Balls III
v
3
t
v
2
You drop a very bouncy rubber
ball. It falls, and then it hits
the floor and bounces right
back up to you. Which of the
following represents the v vs.
t graph for this motion?
t
t
4
v
t
Initially, the ball is falling down, so
its velocity must be negative (if UP
is positive). Its velocity is also
increasing in magnitude as it falls.
Once it bounces, it changes
direction and then has a positive
velocity, which is also decreasing as
the ball moves upward.
Module 2, Recitation 2
Match the s-v-a vs. t graphs of Pasco car motion
Track 1: Level track, spring plunger on one end and Velcro on the
other. Start the car in the center of the track and give it a gentle push
towards the end with the plunger. Plot graphs for the motion from when
you finish pushing the car until it stops.
Insert graph from Data Studio of
position-velocity-acceleration
Track 2: Level track, fan accessory. Start car at left end. The fan is set
to be on for 1 second. Plot graphs for the motion from when the fan
starts until the car reaches the right end of the track.
Insert graph from Data Studio of
position-velocity-acceleration
Track 3: Inclined track, spring plunger. Let the car roll down the track
and bounce off the end several times.
Insert graph from Data Studio of
position-velocity-acceleration
Track 4: Inclined track; small, and large sails. Plot the motion from
when released until the car reaches the end of the track. Compare
motion for no sail (track 3), the small sail, and the large sail.
Insert graph from Data Studio of
position-velocity-acceleration
Module 2, Recitation 2
Match the amusement park acceleration graphs
Mr Hyde
Acceleration
C
Time
Acceleration
Bounty
A
Time
Double Loop
Acceleration
D
Time
Superman Ultimate Escape
Acceleration
F
Time
Villain
Acceleration
B
Time
Drop Zone
Acceleration
E
Time