PhET Projectile Motion Lab

Google “PhET Projectile”, it will be the first hit

(if you NEED a URL, it’s

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. This is a misleading piece of information, as it doesn’t actually tell us height above the ground. 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.

a)Fire the projectile launcher straight upwards (angle = 90o) at 18 m/s. What is the maximum height the ball reached?

d=______

b)Determine the total flight time.(Show your work below!!!)

t=______

In order to calculate the time it took the ball to go from the turning point to the ground, divide t in half.

t/2=______

c)Using the equation: d=1/2*g*t2, (only use half the flight time for your calculation) make sure your calculation for the height of the ball matches part a. (Show your work below!!!)

  1. 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?
  1. 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)
10o / 18
20o / 18
30o / 18
40o / 18
50o / 18
60o / 18
70o / 18
80o / 18
90o / 18

b)What is the best angle for maximum height and air time? Explain why this is so.

c)Which of your angles above gave the most range? Explain why you think this is so.

d)Rank your angles above from smallest to largest x-component of their velocities.

  1. Raise your cannon up into the air by dragging it up (see picture at right). Set it to a height of 12 m (use the tape measure to confirm that it’s 12 m high) Set the launch angle to 00 and the initial speed to 10 m/s. Fire the cannon.

a)What was the air time (the time the projectile was in the air) for that object?

b)Fill in the table below.

Launch Angle / Initial Speed (Vx) (m/s) / Air Time (t) (s)
00 / 10
00 / 12
00 / 14
00 / 16
00 / 18
00 / 20

c) What can we conclude about the air time of objects launched horizontally at different speeds?

  1. Now let’s calculate the RANGE (the distance the projectile was launched) of your object. We know how long your object was in the air, now let’s use that to calculate the distance it traveled. A handy equation to do that would be: vx=d/t, however, you will need to solve for distance (d). (Show your work below!!!)

Initial Speed (Vx) / Range (m)
10
12
14
16
18
20
  1. Suppose we were back in medieval times and we had a cannon. Our castle was located at the top of a cliff, but we weren’t sure how tall it was. We tested this out by dropping a rock and noticed that it took 4.8 seconds to hit the ground below. How high is the cliff? (Show your work below!!!)

d=______

  1. You decided you were going to fire your cannon as soon as your enemies were 50 m away from the base of the cliff. What velocity do you have to fire your cannon at in order to hit them? (Show your work below!!!)

v=______

  1. Oh no, you missed, now they are 35 m away!!! (They can march fast) What velocity do you have to fire a cannon ball now? (Show your work below!!!)

v=______

  1. Now they are climbing the cliff. You decide to drop a cannon ball on their heads. You let the ball go and it only takes 2.1 s to hit them, how close are they? (what is their distance?) (Show your work below!!!)

d=______

  1. What is another force we forgot to take into account, which might have accounted for us missing our enemies with the cannon?
  1. Draw a free-body diagram of a cannon ball flying through the air. Label all the forces acting on the cannon ball.