Projectile and Marble

Freshman Physics Name:_________________________________ Per:____
LAB: Marble Launcher Due Date:_________________

You have learned that the motion of any object moving through the air affected only by gravity is an example of projectile motion. Examples of projectile motion include a basketball thrown toward a hoop, a car driven off a cliff by a stunt person, and a marble launched from the CPO marble launcher. Toss a ball some distance and you can imagine in your mind the arc it follows, first rising then falling to the ground. Projectile motion is also called two-dimensional motion because it depends on two components: vertical and horizontal. The range is the horizontal distance that the projectile travels between launch and landing. In this experiment, you will see how the range is related to the launch angle and initial velocity of launch.

PURPOSE: Which launch angle will produce the greatest range? Which initial velocity of launch will produce the greatest range?

HYPOTHESIS:

VARIABLES:
Independent:______________________________________________
How do you know this?

Dependent:________________________________________________
How do you know this?

MATERIALS
Marble launcher
Graph Paper
Carbon paper
8m tape measure
Timer and photogate
Computer paper
3m high by 7m long space to work
Goggles

THE MARBLE LAUNCHER

TO LAUNCH: Flick the lever out of the slot with your thumb

PRE LAB ANALYSIS: Analyzing the motion of the marble in two dimensions

How can you predict the range of the marble? Since gravity pulls down and not sideways, the motion of the marble must be separated into components. The diagram below shows the velocity of the marble (v) at three points in its trajectory, resolved into x and y components, vx and vy.

a. Use the diagram above to explain why projectiles travel in a curved path called a trajectory.

b. How does the marble’s velocity in x change over the time of the flight? How does its velocity in y change over the time of flight? Explain your findings.

PROCEDURE
1. Set up by marking a tape line on the floor. This is where you will set the front edge of the launcher.
2. Attach the photogate to the front of the marble launcher so that the marble passes directly through the light beam. The photogate attaches to the tab on the end of the wood piece that supports the barrel.
3. Connect the photogate to input A on the timer. Put the timer on “interval” mode.
4. Line the front stand of the marble launcher up with the tape line.
5. One person launches while several group members stand to either side to spot where the marble first touches down.

PART A – RANGE VS. ANGLE OF LAUNCH
6. Place a marble in the barrel and then pull the pin back and slide it into the third of the five slots.
7. Adjust the angle to 30 degrees.
8. Use your thumb to flick the pin out of the slot and launch the marble. DO NOT SHOOT THE MARBLES AT OR IN THE DIRECTION OF ANYONE!
9. Use only the black plastic marbles and obey safety rules.
10. Spotting the landing is tricky. It often takes several launches with the same setup to locate the landing point precisely. For each setup, you may need to run several trials until the measured range is consistent within 10 cm.
11. Taping a piece of paper with carbon paper on top of it at the approximate site of landing will help you be more exact with your measurements.
12. You also want to be consistent with your time. Practice until your times are about 0.0002 seconds from each other (for each angle).
13. You will first keep the marble launcher on spring setting 3 and adjust the launch angle between 10 and 90 degrees.
14. Measure the range, in m, produced from each angle and record three trials in the table.

PART B – RANGE VS. INITIAL VELOCITY OF LAUNCH
15. Place a marble in the barrel and then pull the pin back and slide it into the first of the five slots.
16. Adjust the angle to 30 degrees.
17. Use your thumb to flick the pin out of the slot and launch the marble. DO NOT SHOOT THE MARBLES AT OR IN THE DIRECTION OF ANYONE!
18. Use only the black plastic marbles and obey safety rules.
19. Spotting the landing is tricky. It often takes several launches with the same setup to locate the landing point precisely. For each setup, you may need to run several trials until the measured range is consistent within 10 cm.
20. Taping a piece of paper with carbon paper on top of it in the approximate site of landing will help you be more exact with your measurements.
21. You also want to be consistent with your time. Practice until your times are about 0.0002 seconds from each other (for each spring setting).
22. You will keep the marble launcher at 30 degrees and adjust the initial velocity (spring setting) between notch 1 and 5, with three trials of each.
23. Measure the range, in m, produced from each spring setting and record three trials in the table.

DATA

TABLE I- Range versus Angle Data

Launch
Angle
(degrees)
Distance (m)

T1 T2 T3 AVE

Launch
Angle (degrees)
Distance (m)

T1 T2 T3 AVE
10

50

20

60

30

70

40

80

45

90

TABLE II – Range versus Spring Setting (Initial Velocity) Data

Spring
Setting
Width of Marble (m)

Time (s)
Initial Velocity
(m/s)
Range (m)

T1 T2 T3 AVE
1
0.019

2
0.019

3
0.019

4
0.019

5
0.019

GRAPHS
Make a graph of range vs. launch angle.
Make a graph of range vs. initial velocity
Follow all the “rules” for good, scientific graphs

ANALYSIS QUESTIONS
PART A – RANGE VS. ANGLE OF LAUNCH
1. Where along the trajectory is the vertical component of the velocity of the marble zero? Circle this place on the marble’s path.

2. What angle(s) launched the marble the farthest? Did this surprise you? Why or why not?

3. Compare the range of your marble when launched at 10 degrees and 80 degrees. Explain.

4. You are challenged to launch a marble to travel a distance of 3.00m. Using your graph, at what angle will you set the launcher? What other angle would give you the same result?

PART B – RANGE VS. INITIAL VELOCITY OF LAUNCH
5. What initial velocity (velocities) launched the marble the farthest? Did this surprise you? Why or why not?

6. Compare the range of your marble when launched at 1 notch vs. 5 notches. Explain.

7. You are challenged to launch a marble to travel a distance of 3.00m. Using your graph, at what initial velocity (notch) should you set the launcher?

PART C – PUTTING IT ALL TOGETHER
8. The marble launcher is set up with an initial angle of 30 degrees. The timer reads 0.0030 seconds for the marble with a diameter of 0.019m.
a. Calculate the initial velocity (in m/s) of this marble.

b. Using your graphs, what range would you expect this marble to have in meters?

9. A marble launcher is set up on the floor using notch 3 and an angle of 45 degrees. The marble is launched and the range is measured. The launcher is then taken off the floor and put on a nearby table. It is again set for notch 3 and 45 degrees.
a. Will they travel the same horizontal distance? Explain.

b. Will they travel the same vertical distance? Explain.

c. Will they be in the air the same amount of time? Explain.

10. What are some possible sources of error for this lab? Explain.

11. Write a conclusion paragraph that supports or refutes your hypotheses based on your experimental data. (staple separate sheet of paper to this lab!!)