Question

Apparatus: Spring loaded projectile launcher 5/8" ball bearings Ball loader (plastic rod) Long sheet of paper Carbon paper . trigger string plumb line . Meter stick Safety goggles load here Fig. 1.1-The projectile launcher Procedure: Place a single ball bearing into the launcher (shown in Fig. 1.1), and push it using the ball loader until you hear a click. This is the first speed setting, speed "A". Safety: All students must wear safety glasses. Never look into the barrel of the launcher when it is loaded The experimental setup required to measure the projectile range is shown in Fig. 1.2. Pull the trigger string and note where the ball lands on the paper. Place a piece of carbon paper on the long sheet of paper at this point, dark side down. Repeat the experiment- the projectile will leave a dark mark on the paper where it lands. Remove the carbon paper and label the point. Make sure the table is clear of obstructions before launching a projectile. Projectiles may bounce or roll after striking the table. Be prepared to stop errant projectiles. Don't shoot your instructor or fellow students! 1) First data point Tape your long sheet of paper to the table, aligned with the projectile launcher. Carefully measure the distance from the projectile launcher to the point of impact, and record the range in your lab report. Loosen the back thumbscrew on the projectile launcher and use the plumb line to set the launch angle θ to 15° above the horizontal. Tighten the thumbscrew 2) Repeat for second speed Keep the apparatus at 15°. When loading the projectile launcher, push the projectile until you hear two clicks. This is the second speed setting, speed "B", faster than the first. Using the same method described in part 1, measure the projectile range for this higher launch speed. Record the range in your lab report. You will not use the third speed setting in this lab. X1-2

Experimental technique

5. [1pt]
Which of the following statements are true for this experiment? E.g., enter AB. If none are true, enter N. You have 4 tries.

Everyone must wear safety glasses.

For each launch angle, the projectile range is measured for one speed setting.

Never look into the barrel of the launcher when it is loaded.

The launch angle θ measured using the plumb line is the angle of the launcher with respect to the vertical.

The projectile is launched from zero height on the table.

Answer:  Last Answer: ABC
Incorrect, tries 2/4.

Calculated uncertainty

A projectile is launched through a photogate to determine its speed. The projectile is measured to be 19.0 ± 0.2 mm across, and it blocks the photogate sensor for 6.59 ± 0.02 ms.

6. [1pt]
Calculate the speed of the projectile.

Answer:  

7. [1pt]
Calculate the uncertainty in the speed of the projectile.

Answer:  

Experimental uncertainty

8. [1pt]
The diagram shows the impact of 21 projectiles launched at the same speed and angle. What is the uncertainty in the impact position?

Note: These data were collected using the same apparatus you will use in the lab. The uncertainty you find for this question is what you should use for your experimental data.

Answer:  

Graphs

9. [1pt]
A student measured the range of a projectile launched at the same speed but different launch angles. The measured range had some uncertainty. Which of the following are acceptable graphs? (See Appendix B of your lab manual for a good-graph checklist.) E.g., enter AB.

A)			B)
C)			D)

Answer:  

Analyzing non-linear data


A student found the following range vs. angle data for a projectile motion experiment.
Using graph paper, plot a graph of range vs. θ. This graph is non-linear! To linearize the data, complete the table and draw a graph of range r vs. sin(2θ).
Note: The following questions can only be solved by first plotting a linear graph. If you don't draw an accurate graph, your answers will be incorrect! There are no shortcuts.

Launch angle θ (deg)	sin(2θ)	range r (m)
0		0.00 ± 0.03
15		0.20 ± 0.03
30		0.35 ± 0.03
45		0.44 ± 0.03
60		0.38 ± 0.03
75		0.23 ± 0.03
90		0.00 ± 0.03

10. [1pt]
What is the slope of the best fit line?

Answer:  

11. [1pt]
What is the uncertainty in the slope?

Answer:  

12. [1pt]
What was the projectile speed?

Answer:  

13. [1pt]
What is the uncertainty in the speed?

Answer:  

Conclusions

14. [1pt]
Which of the following should be included in your Conclusions? (See page xi in your lab manual.) E.g., enter AB. You have 4 tries.

If something went wrong, an explanation of why this might have been the case

Comparisons of your results with accepted values, or with your other results, or with other students' results

All your calculations

Did your experimental results agree with the theory?

Your important numerical results

How you feel about the lab

Answer:  

Answer 1

5. the following statements are true

a. Everyone must wear safety glasses.

c. Never look into the barrel of the launcher when it is loaded.

e. The projectile is launched from zero height on the table.

so the answer is a, c, e

6. given measurement of projectile, d = 19 +- 0.2 mm

time , t = 6.59+-0.02 ms

speed of projectile = d/t = 19*10^-3/6.59*10^-3 = 2.883 m/s

7. uncertianity in speed of projectil;e be dv

then dv/v = sqroot((dd/d)^2 + (dt/t)^2)

dv = v*sqroot((0.2/19)^2 + 0.02/6.59)^2)

dv = 0.0315 m/s

8. from the plot of projectiles landing position, uncertianity of position is +- 1 cm

as most of the results are under +- 1 cm of 2 cm mark