easy Physics lab worksheet

1

PHY2053C

Module 3 Lab

Projectile Motion

Objective:

· To study projectile motion

· To determine the range and time of flight of a projectile

· To analyze the effect of air-resistance

Procedure:

1. On your computer, open the webpage – http://phet.colorado.edu/en/simulation/projectile-motion

2. Click on the “Run Now” button, located just below the picture of the projectile. That should open up a new window that looks like this

3. If the new window fails to launch, try the “Download” button right next to “Run Now”. Once downloaded, you can double-click on the file to start the simulation. If the simulation still does not run, you most likely need to install “java” in your computer, which you can do for free from the java website - https://www.java.com/en/

4. Once the simulation is running and you come to the screen shown in the picture above, click on the “Fire” button located near the bottom right of the screen. That will fire the cannon and launch the projectile (if you have your computer sound turned on, you will hear some hilarious and really loud sound effects).

5. On the right side of the screen, you have the input parameters – firing angle, initial speed, mass of projectile, diameter of projectile and air resistance. You can change these values. Do so. Try playing with different parameters and fire the projectile several times to get a better idea about how this simulation works. If you click “Erase”, it will erase the projectile trajectories drawn on the screen.

6. On top of the screen, you have the output values – range of the projectile and the time it takes to hit the ground. The “height” can be left to the default value of -1.2 m, which reflects the fact that the target (the red circle on the ground) is 1.2 m below the chamber of the cannon, from where the projectile is launched.

Data and Calculation

A.

1. Click “Erase.”

2. Turn off the “air resistance” if it was on.

3. Use the following values for the input parameters:

angle – 300; speed – 18 m/s; mass – 2 kg; diameter – 0.1 m

DO NOT fire yet.

4. Before firing, calculate the range and time for the projectile.

In other words, find out how far the projectile will travel and

for how long, before it hits the ground (which is 1.2 m below

the launching point).

Range ___________ Height -1.2 m Time ___________

5. Now, fire the projectile. What is the actual range and time?

Range ___________ Height -1.2 m Time ___________

6. If your calculated answer was wrong, find out why.

B.

1. Click “Erase.”

2. Change the input angle to 450; leave everything else unchanged.

3. Before firing, Calculate the range and time for the projectile

Range ___________ Height -1.2 m Time ___________

4. Now, fire the projectile. What is the actual range and time?

Range ___________ Height -1.2 m Time ___________

5. If your calculated answer was wrong, find out why.

C.

1. DO NOT “Erase.”

2. Select some random values for input angles, for example - 600, 250, 850, 370, etc. Fire the projectiles at these different angles (without erasing). Do the trajectories show that projectile launched at any angle other than 450 will travel less?

D.

1. Click “Erase.”

2. Leave everything else unchanged, only change the mass of the projectile several times and fire. Does the mass of the projectile affect its motion? (If two different trajectories are exactly identical and you didn’t erase the first trajectory, then you won’t see the second one).

3. Erase. Leave everything else unchanged, only change the diameter of the projectile several times and fire. Does the diameter of the projectile affect its motion?

E.

1. Turn the “Air Resistance” ON. Leave the “drag coefficient” 1 and “altitude” 0.

2. Click “Erase”

3. Leave everything else unchanged, only change the mass of the projectile several times and fire. Does the mass of the projectile affect its motion in presence of air-drag? Does the range increase or decrease with increasing mass?

Does the time increase or decrease with increasing mass?

What happens if you select a very small mass (0.02 kg for example)? Explain.

4. Erase. Change the mass back to 2 kg. Leave everything else unchanged, only change the diameter of the projectile several times and fire. Does the diameter of the projectile affect its motion in presence of air-drag?

Does the range increase or decrease with increasing diameter?

Does the time increase or decrease with increasing diameter?

What happens if you select a very large diameter (1 m for example)? Explain.

F.

1. Click “Erase.”

2. Change the diameter back to 0.1 m, mass 0.5 kg and drag coefficient 10. Is the maximum range still achieved at 450 launch angle? If not, is the angle that gives the maximum range, greater or lesser than 450?