Lab: Projectile Motion (Marble Drop) (18 points) (page 1 of 2)
You have probably watched a marble roll off a table and strike the floor. What determines where it will land? In this study, you will roll a marble down a ramp and determine the marble’s velocity with a pair of photogates. You will use this information and your knowledge of physics to predict where the marble will land when it hits the floor.
Materials
LabPro interface
IBM compatible PC marble plumb bob ramp ring stand & clamp meter stick
LoggerPro program
2 photogates masking tape
Procedure:
1. Set up a ramp made of angle molding on a table so that a marble can roll down the ramp, across a short section of table, and off the table edge as shown above..
2. Position the photogates on the flat table. The marble should roll through the center of each photogate and not touch the sides. Mark a start position on the ramp for the marble. Test the setup by rolling the marble down the ramp. Once you are satisfied, tape things in place. Any movement will mess-up the results.
3. Connect photogate 1 to DIG/SONIC 1 and photogate 2 to DIG/SONIC 2 .
4. Open the file in the Experiment 8 folder of Physics with Computers. One graph should display the time for the marble to pass through the photogates. A second graph should display the velocity through the photogates.
5. Carefully measure the distance from photogate 1 to the photogate 2. (Distance from similar edge to similar edge.) Enter the distance into Logger Pro by selecting Data Collection from the Setup menu, then clicking the Sampling tab. Change the number in the Distance Between Gates field to the correct distance in meters. Click
.
8 to 10 cm
6. Click . Test the photogates . Move your finger through gate 1 and then gate 2. Logger Pro should plot the time to go between the gates.
Click system.
, then click to reset the photogate 1
Figure 2 photogate 2
7. Roll the marble down the ramp until you have recorded 10 consistent velocity readings.
After the last trial, click to end data collection. Calculate the average velocity.
8. Record the distance from the table top to the floor. Use a plumb bob to locate the point on the floor just beneath the point where the marble will leave the table. Mark this point with tape; it will serve as your floor origin .

Students in team: _________________________________________________ period _____
Lab: Projectile Motion (Marble Drop) (18 points) (page 2 of 2) plumb bob f loor origin
Figure 3
9. Use h = 0.5gt
2
to calculate the time the marble is in the air. Use x = v x t to calculate distance from floor origin to the impact point. Mark this predicted impact point on the floor with tape.
10. Have your instructor observe a marble drop. They will initial your lab and record the actual observed landing distance.
Data Tables: (14 points)
Trial Velocity
(m/s)
1
2
3
4
Maximum velocity
Minimum velocity
Average velocity
Table height
5
6
7
8
9
Time marble is in air t = (2h/g)^0.5
Predicted impact point x = v x t
Teacher initials
Actual impact point distance
10
Analysis: Show a calculation for % error. (4 points) s m m m/s m/s m/s m