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PhET Projectile Motion Lab
Google “PhET Projectile”, it will be the first hit
(if you NEED a URL, it’s http://phet.colorado.edu/en/simulation/projectile-motion)
Then click the button beneath the picture. Take a
few minutes to familiarize yourself with the simulation and
shoot stuff with the cannon. Once you’ve somewhat satisfied
your primal desires to shoot things, follow along with the
questions below. Use complete sentences, yo.
1. Look at the “height” box at the top. What kinematics term does it actually stand for, and what point is it relative to? (hint: shoot the cannon once and watch the number closely). Explain your reasoning. 2. Fire the projectile launcher straight upwards (angle = 90o) at 18 m/s. Using kinematics, determine: a) the time it should take the projectile to reach maximum height
b) the maximum height reached by the projectile
c) Now, using the measuring tape, measure the actual height reached by the projectile (remember to measure from the little plus sign at the base of the cannon). Was your answer to (b) the same as this measurement? If it wasn’t, check your math over and find your mistake.
3. Pick any initial speed and launch angle, and try out firing all the different objects (golfball -> Buick). How does the mass of an object affect its motion through the air? 4. You are now going to investigate the effect of launch angle on several different parameters; air time, maximum height, and range. a) Fire the projectile launcher at the following angles (with the same initial speed of 18 m/s), then fill in the table below. You will need to use the measuring tape to measure the maximum height and the range.
Angle Initial Speed (m/s)
Air Time (s)
Maximum Height (m)
Range (m)
10 o^18 20 o^18 30 o^18 40 o^18 50 o^18 60 o^18 70 o^18 80 o^18 90 o^18
b) What is the best angle for maximum height and air time? Explain why this is so.
c) Is there a direct relationship between air time and range? Explain why or why not. This is an important question, make sure to give it some serious thought.
d) Which of your angles above gave the most range? Explain why you think this is so.
e) Rank your angles above from smallest to largest x -component of their velocities. Is there a direct relationship between the x -velocity of a projectile and its range? Explain why or why not.
6. Reset the cannon back to the ground. This time, check the box. You can leave the drag coefficient and altitude at 1 and 0 where they are by default. Keep the red target on the x -axis as it was before. Start with the tankshell as your projectile. a) What effect does the mass of an object have on the maximum height and range when air resistance is turned on? Explain.
b) What is the best angle for maximum range for the tankshell at an initial speed of 18 m/s when air resistance is turned on? Is this result different than when there was zero air resistance? Explain your results.
c) Find the best angle for maximum range when dy = 0 (when the object hits your target) with four different objects. Record this information in the table below: Object Mass (kg) Angle for maximum range
7. Challenge time: Solve the problems below. They are about pirates… just because.
a. Consider this scenario and ignore air resistance. A pirate fires his cannon parallel to the water but 3.5 m above the water. The cannonball leaves the cannon with a velocity of 120 m/s. He misses his target and the cannon ball splashes into the briny deep. How far did the cannonball travel? (please show work)
b. A rival pirate fires his volley back at the same 3.5 m above the sea, but at an angle of 23^0. Coincidentally, this scurvy dog’s cannon also fires at 120 m/s. Also strangely coincidentally, this cannonball also misses and splashes into the sea. How far did this cannonball travel? (please show work)(Hint: To figure out time, you will have to use the quadratic equation). (If you can do this correctly… you will get 5 points of extra credit).
