Physics lab 3 - Projectile motion lab PDF

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Projectile motion lab
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Thidalis Theapanha PHYS 1410L Section 807 TA Vishnu Chavva October 24, 2020

Lab 3 Projectile Motion Objective: To study, predict, and quantify the motion of objects in a projectile motion. Initial velocity and angle of the projectile will be important to the maximum range and height of the motion.

PhET Projectile Motion Lab Search for “PhET Projectile”, it should be the first hit Or use this link: http://phet.colorado.edu/en/simulation/projectile-motion

Click the download button beneath picture. Double click on the ‘Lab’ button in the opening screen. Take some time to familiarize yourself with the simulation, i.e. learn how to use all of the options by trying out different possible parameters. Note the zoom buttons at the upper left of the screen and the measuring tool.

1. Look at the “height” in the measuring tool at the top. What “linear motion” term does it actually stand for? Hint: shoot the cannon once and watch the height number closely: distance (scalar) or displacement (vector) displacement of y 2. Look at the “range” in the measuring tool at the top. What “linear motion” term does it actually stand for? displacement of x 3. Move the projectile launcher up 5 m from the ground. Using the cannon ball, fire the projectile launcher straight upwards (angle = 90o) at 15 m/s. Record the following information using the measuring tool: a) Total time in the air. 3.36s b) Maximum height reached. 16.47 m c) Total horizontal displacement. 0m d) Total vertical displacement. -5m

4. Pick any initial speed other than 15 m/s. Be sure that your parameters allow you to measure the range. Make the following measurements.

I used 1m for initial height but it still answers the question. Golf Ball —2 trials at 2 different angles: Time: 1.77s Time: 1.56s Time: 1.77s Time: 1.56s Range: 8.83m

Range: 10.04m

Max Height: 3.82m Max Height: 3.82m

Tank Shell ---2 trials at 2 different angles:

Range: 8.83m

Range: 10.04m

Max Height: 2.99m

Mass: 0.01kg

Mass: 42kg

From your results describe how the mass of the projectile affects it motion. Mass of the projectile does not affect its motion 5. Next let’s investigate the effect of the launch angle on several different parameters: time (in the air), range, and maximum height. a) Fire the projectile launcher using the cannonball at the following angles (with the same initial speed of 18 m/s and any other variables that default), then fill in the table below. You will need to use the measuring tape to measure the maximum height and the range. Angle (deg)

Initial Speed (m/s)

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18

Time (s)

Range (m)

Max Height (m)

1.55 1.83 2.1 2.36 2.59 2.81 3.01 3.18 3.33 3.45 3.54 3.61 3.66 3.67

25.3 28.6 31.04 32.53 33.03 32.53 31.04 28.6 25.3 21.23 16.51 11.3 5.74 0

2.95

4.13 5.43 6.82 8.26

9.69 11.08 12.38 13.56 14.58 15.41 16.02 16.39 16.51

b) From your results what is the best angle for maximum height and maximum time in the air? 90 degree c) Is there a direct relationship between time in the air and the range? {It is suggested that you make a plot.} Justify the relationship if you can.

Time vs Range 35 30

Range

25 20 15 10 5 0

1

1.5

2

2.5

3

3.5

4

Time

The range decreases as time increases after maximum range is reached. d) Which angle(s) gave the largest range? Explain why you would have expected this result. 45 degree because it is has the most velocity in both x and y direction. e) Look at your data and find all the pairs of launch angles that add up to 90 degrees. Compare the range for each pair. Why do you get this result? the range for each pair that add up to 90 degrees are the same. This happens because they are complementary angles since they have the same difference from 45 degrees. 6. Use a mass at 5 kg for the cannon ball and set the launch angle to 25°. Use initial speeds of 10, 15 and 20 m/s. a) Note what happens with the initial velocity (vi) and record: Initial Speed Time Range

10

0.36

7.81

15

1.29

17.57

20

1.72

31.24

1. Does varying the initial speed affect your results for time and range? Why do you think this is the case? Yes, as velocity increases time and range also increase because there is more initial velocity in both the x and y direction. 2. Describe the shape of trajectories for the different initial speeds. The shape of the trajectories look like parabolas, just with different ranges. b) What effect does doubling the initial speed/velocity have on the range of the projectile? Explain your results. [Change the velocity to 60 m/s and compare your results with the 30 m/s results.]

When the initial velocity is doubled the range of the projectile quadripled. 31.24/7.81=4 7. Reset the projectile launcher back to the ground. Check the box. You can leave the drag coefficient and altitude at their default values. Start with the cannon ball projected at 45 degrees. a) Vary the mass and see what effect it has on the maximum height and range (with air resistance turned on). Compare this to having no resistance. Explain your results. The greater mass changes the maximum height and range negatively when there’s air resistance and positively when there is no resistance. b) What is the angle that gives the maximum range for the cannon ball at an initial speed of 25 m/s with air resistance turned on? Is this result different than when there was zero air resistance? Explain your results. The angle that gives the maximum range is 45 degree for when there is air resistance and zero air resistance. c) Find the best angle for maximum range (with air resistance) for four different objects having different masses. Record this information in the table below: Object cannonball

Mass (kg) 17.60

Angle for maximum range 45

Tank shell

5

45

Golf ball

0.05

45

Baseball

0.15

45

d) Is the angle for maximum range dependent on the mass of an object when air resistance is turned on? The mass does not affect the angle for maximum range when air resistance is turned on. 8. Conclusion Briefly summarize the different aspects of projectile motion that were studied in this lab experiment (ex. how does the maximum height depend on the initial velocity). This should include the specific equations that particularly apply to projectile motion. From this lab experiment, the different aspects that were studied are:  the mass of the projectile does not affect its motion,  the range of the complimentary angles are the same,  the mass does not affect the angle for maximum range when air resistance is turned on, and  the initial velocity affects both the x and y direction of the motion. Initial velocity involvement with maximum is also proven by the formula: ymax=v02sin2theta/2g Discussion

The results from the table proved that the mass does not affect its motion and that the range of complimentary angles are the same. The lab could have been less confusing if the instructions on what height and what angles to start with are clearer. Conclusion The mass theory was met by the experiment where two different masses are projected from the same angle, initial velocity, and height. The range theory was met by the different angles experiment and 45 degree angle was proven to be the angle that provides the maximum range and height for the projectile motion since the other angles provided less height and range. AT-HOME ACTVITY Procedures for At-Home Activity (Basketball Bounce) Download “Tracker”: https://physlets.org/tracker/ Open “Tracker” (help link): https://www.physlets.org/tracker/tracker_help.pdf Drag video (supplied in Blackboard) into display. (You may make your own video instead.) Set clip settings – identify start/stop frames and step size (try 3). Calibrate the scale – use stick – diameter of the basketball equals 0.24 m. Set reference frame origin on first frame to be used. Track the motion – use point mass; hold down shift key and click mouse. Turn on velocity and acceleration vectors.

Suggestions for analysis of the motion: Determine average acceleration, compare to your expectation. Average acceleration= 2.337-10.31/0.9-0.1=-9.96625. My expectation for average acceleration for this motion was something close to -9.8 and -9.97 is close enough. Capture a few plots (views can be changed). Explain the plots.

I set the diameter of the ball to 0.24 m with a cabrilation stick. The axis is at the center of the ball of the first frame. Summarize what you conclude about the motion. The motion is in the shape of a parabola. The ball has velocity in both the x and y direction. The velocity of the ball decreases as it reaches the maximum height of the motion....