module 2, recitation 2
DESCRIPTION
Module 2, Recitation 2. Concept questions on v-t graphs. x. t. ConcepTest Graphing Velocity I. 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. - PowerPoint PPT PresentationTRANSCRIPT
Module 2, Recitation 2
Concept questions on v-t graphs
ConcepTest Graphing Velocity I
t
x
The graph of position versus The graph of position versus
time for a car is given below. time for a car is given below.
What can you say about the What can you say about the
velocity of the car over time?velocity of the car over time?
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
ConcepTest Graphing Velocity I
t
x
The graph of position versus The graph of position versus
time for a car is given below. time for a car is given below.
What can you say about the What can you say about the
velocity of the car over time?velocity of the car over time?
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!
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
t
x
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 graph of position vs. The graph of position vs.
time for a car is given below. time for a car is given below.
What can you say about the What can you say about the
velocity of the car over time?velocity of the car over time?
ConcepTestConcepTest Graphing Velocity IIGraphing 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
t
x
The graph of position vs. The graph of position vs.
time for a car is given below. time for a car is given below.
What can you say about the What can you say about the
velocity of the car over time?velocity of the car over time?
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.
ConcepTestConcepTest Graphing Velocity IIGraphing Velocity II
Consider the Consider the vv versus versus tt
plot. How does the plot. How does the
speed change with time?speed change with time?
v
t
1) decreases1) decreases
2) increases2) increases
3) stays constant3) stays constant
4) increases, then decreases4) increases, then decreases
5) decreases, then increases5) decreases, then increases
ConcepTestConcepTest vv versus versus tt graphs I graphs I
Consider the Consider the vv versus versus tt
plot. How does the plot. How does the
speed change with time?speed change with time?
v
t
1) decreases1) decreases
2) increases2) increases
3) stays constant3) stays constant
4) increases, then decreases4) increases, then decreases
5) decreases, then increases5) decreases, then increases
The initial velocity is positive and the magnitude of the velocity continues to increase with time.
ConcepTestConcepTest vv versus versus tt graphs I graphs I
Consider the Consider the vv versus versus tt
plot. How does the plot. How does the
speed change with time?speed change with time?
v
t
1) decreases1) decreases
2) increases2) increases
3) stays constant3) stays constant
4) increases, then decreases4) increases, then decreases
5) decreases, then increases5) decreases, then increases
ConcepTestConcepTest vv versus versus tt graphs II graphs II
Consider the Consider the vv versus versus tt
plot. How does the plot. How does the
speed change with time?speed change with time?
v
t
1) decreases1) decreases
2) increases2) increases
3) stays constant3) stays constant
4) increases, then decreases4) increases, then decreases
5) decreases, then increases5) decreases, then increases
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.
ConcepTestConcepTest vv versus versus tt graphs II graphs II
ConcepTest Rubber Balls Iv
t1
v
t2
v
t3v
t4
You drop a rubber ball. Right after it You drop a rubber ball. Right after it
leaves your hand and before it hits the leaves your hand and before it hits the
floor, which of the above plots floor, which of the above plots
represents the represents the v v vs.vs. t t graph for this graph for this
motion? (Assume your y-axis is motion? (Assume your y-axis is
pointing up).pointing up).
ConcepTest Rubber Balls Iv
t1
v
t2
v
t3v
t4
You drop a rubber ball. Right You drop a rubber ball. Right
after it leaves your hand and after it leaves your hand and
before it hits the floor, which of before it hits the floor, which of
the above plots represents the the above plots represents the
v v vs.vs. t t graph for this motion? graph for this motion?
(Assume your y-axis is pointing (Assume your y-axis is pointing
up).up).
The ball is dropped from rest, so its
initial velocity is zeroinitial velocity is zero. Since the y-axis
is pointing upwards and the ball is
falling downwards, its velocity is velocity is
negativenegative and becomes more and more more and more
negativenegative as it accelerates downward.
v
t4
v
t2
v
t3
v
t1
You toss a ball straight up in the air You toss a ball straight up in the air
and catch it again. Right after it and catch it again. Right after it
leaves your hand and before you catch leaves your hand and before you catch
it, which of the above plots represents it, which of the above plots represents
the the v v vs.vs. t t graph for this motion? graph for this motion?
(Assume your y-axis is pointing up).(Assume your y-axis is pointing up).
ConcepTestConcepTest Rubber Balls II
v
t4
v
t2
v
t3
v
t1
You toss a ball straight up in You toss a ball straight up in
the air and catch it again. the air and catch it again.
Right after it leaves your hand Right after it leaves your hand
and before you catch it, which and before you catch it, which
of the above plots represents of the above plots represents
the the v v vs.vs. t t graph for this graph for this
motion? (Assume your y-axis motion? (Assume your y-axis
is pointing up).is pointing up).
The ball has an initial velocity that is initial velocity that is
positivepositive but diminishing as it slows. It
stops at the top (v = 0), and then its
velocity becomes negativevelocity becomes negative and
becomes more and more negativemore and more negative as it
accelerates downward.
ConcepTestConcepTest Rubber Balls II
v
t1
v
t2
v
t3v
t4
ConcepTestConcepTest Rubber Balls III
You drop a very bouncy rubber You drop a very bouncy rubber
ball. It falls, and then it hits the ball. It falls, and then it hits the
floor and bounces right back up to floor and bounces right back up to
you. Which of the following you. Which of the following
represents the represents the v v vs.vs. t t graph for graph for
this motion?this motion?
v
t1
v
t2
v
t3v
t4
You drop a very bouncy rubber You drop a very bouncy rubber
ball. It falls, and then it hits ball. It falls, and then it hits
the floor and bounces right the floor and bounces right
back up to you. Which of the back up to you. Which of the
following represents the following represents the v v vs.vs.
tt graph for this motion? graph for this motion?
Initially, the ball is falling down, so its velocity must be negativenegative (if UP is positive). Its velocity is also increasingincreasing in magnitude as it falls. Once it bounces, it changes direction and then has a
positivepositive velocity, which is also
decreasingdecreasing as the ball moves upward.
ConcepTestConcepTest Rubber Balls III
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
Time
Ac
ce
lera
tio
n
C
Bounty
TimeA
cc
ele
rati
on A
Double Loop
TimeA
cc
ele
rati
on D
Superman Ultimate Escape
Time
Ac
ce
lera
tio
n
F
Villain
TimeA
cc
ele
rati
on B
Drop Zone
Time
Ac
ce
lera
tio
n E