Interactive Lecture Demonstration
Prediction Sheet—Projectile Motion
Directions:
Click here to download the Prediction Sheet,
which you may be asked to turn in to your instructor. Follow the instructions,
and always be sure to make your predictions before making observations.
These demonstrations involve a ball
thrown in the air with an initial velocity upward and to the right. First
observe the motion by clicking BallToss
to download and then play the video. As you see in the video, the trajectory of the ball looks
approximately like the sketch to the right.
Note that the origin of the coordinate system has been chosen to be
the initial position of the ball. 



Demonstration 1: Sketch on the
axes on the right your predictions for the x coordinate of the ball as a function of time and the y
coordinate of the ball as a function of time. Only after you
have made your predictions, click Position to
display a video with the Positiontime graphs plotted out as the ball
moves. Compare the actual x and y position
graphs to your predictions and explain any differences. Based on your
graph of x vs. t, write a kinematic equation for x as a function of time. Based on your
graph for y vs. t, write a kinematic equation for y as a function of time. 


Question
1: When is
the speed of the ball a maximum? A minimum? Question
2: At the
highest point in its motion, is the speed of the ball zero? 
Question
3: When is
the xcomponent of the velocity a
maximum? A minimum? Question 4: When is the ycomponent of the velocity a maximum? A minimum? 


Demonstration 2: On the axes to
the right, sketch your predictions for the xcomponent of the velocity as a function of time and the
ycomponent of the velocity as a function of time. Only after you
have made your predictions, click Velocity to
display a video with the Velocitytime graphs plotted out as the ball
moves. Compare the actual vx and vy velocity graphs to your predictions and
explain any differences. Based on your
graph for vx vs. t,
write an equation for vx as a function of time. vx =
______________________ Based on your
graph for vy vs. t,
write an equation for vy as a function of time. vy =
______________________ 


Question 5: In the space below, draw an arrow
that represents the direction of the acceleration of the ball (a) just after
it is released, (b) when it reaches the highest point in its trajectory, (c)
while it is on its way down. If the
acceleration is zero, write ZERO above the ball. Only
after you drawn your arrows, click here to see
the correct answers 


Question 6: In the space below, draw the
freebody (force) diagram for the ball (a) just after it is released, (b)
when it reaches the highest point in its trajectory, (c) while it is on its
way down. If there are no forces acting on the ball, write NONE above the
ball. If the net force on the ball is
zero, write ZERO above the ball Only
after you drawn your arrows, click here to see the
correct answers 

