PHYSICS LABORATORY: Graphing Kinematics
Adapted from: Vernier Physics
Background Information and Purpose
Lots of objects go back and forth; that is, they move along a line first in one direction, then move back
the other way. An oscillating pendulum or a mass on a spring are examples of things that go back
and forth. Graphs of the position vs. time and velocity vs. time for such objects share a number of
features. In this experiment, you will observe a number of objects that change speed and direction as
they go back and forth. Analyzing and comparing graphs of their motion will help you to apply ideas
of kinematics more clearly. In this experiment you will use a Motion Detector to observe and
contemplate the motion of the following objects:
Oscillating pendulum
Ball rolling up and down an incline
Mass oscillating at the end of a spring
Additionally, you will become familiar with motion (kinematics) graphs in this lab.
Data Processing and Collection (DCP)
Part I Oscillating Pendulum
1. Connect the Motion Detector to the DIG/SONIC 1 channel of the interface. If the Motion
Detector has a switch, set it to Normal.
Motion Detector
Figure 1
2. In LoggerPro, open the file “02 Pendulum” from the Physics with Vernier folder. Sketch a
prediction of the position vs. time and velocity vs. time graphs of a pendulum bob swinging
back and forth. Ignore the small vertical motion of the bob and measure position along a
horizontal line in the plane of the bob’s motion. Think: based on the shape of your velocity
graph, do you expect the acceleration to be constant or changing? Why? Will it change
direction? Will there be a point where the acceleration is zero?
3. Place the Motion Detector near a pendulum with a length of 1 to 2 m. The Motion Detector
should be level with the pendulum bob and about 1 m away when the pendulum hangs at
rest. The bob should never be closer to the detector than 0.15 m.
4. Pull the pendulum about 15 cm toward the Motion Detector and release it to start the
pendulum swinging.
5. Click to begin data collection.
6. If you do not see a smooth graph, the pendulum was most likely not in the beam of the Motion
Detector. Adjust the aim and repeat Steps 5–6.
Part II Ball on an Incline
1. If the Motion Detector has a switch, set it to Normal.
2. Place the Motion Detector at the top of an incline that is around 1 m long. The angle of the
incline should be between 5° and 10°.
3. Open the experiment file “02 Cart.” Two graphs will appear on the screen. Sketch your
prediction of the position vs. time and velocity vs. time graphs for a ball rolling freely up an
incline and then back down. The ball will be rolling up the incline and toward the Motion
Detector initially. Think: will the acceleration be constant? Will it change direction? Will there
be a point where the acceleration is zero?
1
4. Hold the ball at the base of the incline. Click to begin taking data. When you hear the
clicking, give the ball a push up the incline. Make sure that the ball does not get closer than
0.15 m to the Motion Detector and keep your hands away from the track as the ball rolls.
5. Zoom in on the portion of each graph that represents the time that the ball was freely rolling.
To do this, use the mouse to drag a rectangle around the useful portion of the data, then click
the Zoom In button, .
Part III A Mass Oscillating at the End of a Spring
1. If the Motion Detector has a switch, set it to Normal.
2. Place the Motion Detector so it is facing upward, about 1 m below a mass suspended from a
spring.
3. Open the experiment file “02 Spring.” Sketch your prediction for the position vs. time and
velocity vs. time graphs of a mass hanging from a spring as the mass moves up and down.
Think: will the acceleration be constant? Will it change direction? Will there be a point where
the acceleration is zero?
4. Lift the mass about 10 cm (and no more) and let it fall so that it moves up and down.
5. Click to begin data collection.
6. If you do not see a smooth graph, the mass most likely was not in the beam of the Motion
Detector. Adjust the aim or look for interfering objects and try again.
7. Zoom in on the portion of each graph that represents one cycle of the mass. To do this, use
the mouse to drag a rectangle around the useful portion of the data and click the Zoom In
button, . Answer the Analysis questions for Part IV before proceeding to Part V.
Conclusion and Evaluation (CE) (All questions 1 mark each)
Part I Oscillating Pendulum
1. Provide the position and velocity graphs for the motion of the pendulum.
2. Was there any point in the motion where the velocity and/or acceleration was zero? Explain.
3. Where was the pendulum bob when the acceleration was greatest? Explain why.
Part II Ball on an Incline
4. Provide the position and velocity graphs that represent the time that the ball was going up and
down the incline.
5. Use a tangent line and the velocity graph to determine the acceleration of the ball when it was
on the way up, at the top, and on the way down the incline. What did you discover?
6. Was there any point in the motion where the velocity and/or acceleration was zero? Explain.
Part III Mass Oscillating on a Spring
7. Provide the position and velocity graphs for the vibration of the mass.
8. Was there any point in the motion where the velocity and/or acceleration was zero? Explain.
9. Where was the mass when the acceleration was greatest? Explain why.
Parts I-III
10. State two features that the three position graphs had in common, and two ways they were
different from one another.
11. State two features that the three velocity graphs had in common, and two ways they were
different from one another.
