Name ____________________________________
Lunar Lander Simulation
Go to http://phet.colorado.edu/simulations/sims.php?sim=Lunar_Lander and click on Run Now.
1) Once the simulation opens, click on ‘Vectors’ before you start. Read the directions and attempt to make a
soft landing. Once you land, describe what you had to do to get the Lunar Lander to land softly. What
happens if you give the Lander too much thrust? What happens if you give it too little thrust?
2) Once you land safely blast off then move left or right to a new landing zone. Describe the sequence of
maneuvers that you must execute to get the Lander to move sideways and then carry out a soft landing that is
nice and vertical.
3) What color is the thrust vector and what color is the velocity vector? How can you tell?
4) When landing, is it better to let the Lander fall most of the way and then turn on the thrusters to maximum
to get it to slow down? Or is it better to have the thrusters on low the whole time to keep the velocity from
building up to much? Explain.
5) You will now attempt to calculate the mass of the lander and to calculate the “ideal” thrust to get the
lander to land. You will eventually use Net F = m*a to do your calculations. First, reset the program and
IMMEDIATELY apply 2250 N of thrust. Using your givens, set up a “Gunk” to find the acceleration of the
Lander. (HINT: look for displacement, time, initial velocity, or final velocity)
a = _____________ m/s2
6) Using the above scenario, draw an FBD of the lander. What forces are acting on it? Which force is the
greatest? How do you know?
7) Recall, if you have a box and there are two people pushing on it from different sides, you should be able
to find the net force. If one person pushes to the left with a force11 N and the other to the right with 6 N,
draw an FBD and then find the net force acting on box.
a) What did you have to do to the two forces acting on the box to find the net force?
b) Now let's focus on the Lunar Lander again. Plug in the weight and the thrust into the equation below:
Net Force = _________ - __________
(Note that you will not know the weight just yet, since you do not know the mass of the Lander)
c) Using the equation above and knowing that Net Force = m*a, fill in the equation below to get a good idea
of how to find the mass of the lander. You will not know all the values so use variables where needed.
Setup the Net Force equation:
_______ - _________ = _________ * ___________
d) Realize that weight = m * g. Your equation should now look like:
___________ - _________ * ___________ = ___________ * ________________
e) From the equation above, substitute in all of the known values. Remember, the value for “g” on the moon
is 1/6 that of Earth’s value. Use the value of thrust (as you were given it on #5) and the value for acceleration
(as you calculated it on #5). Your equation now look like:
___________ - _________ * ___________ = ___________ * ________________
f) Your equation should now only have one variable left, m. Solve for the mass of the lander.
Mass = _________________ kg
8) Calculate the amount of thrust required to allow the lander to fall at a constant velocity. This is referred to
as the “ideal thrust.” It is equal to the weight of the Lander.
Ideal Thrust = _____________ N
9) Test your thrust!: What happens if you apply more thrust than the “ideal thrust?” Try it. Set your thrust
so that it is 1 more setting above your calculated value. What happens to the lunar lander?
What happens if you apply less thrust than the “ideal thrust?” Try it. Set your thrust so that it is 1 setting
below your calculated value. What happens to the lunar lander?
Note: If you land your lander on the surface and then only apply the amount of thrust equal to 1 less setting
than your calculated ideal thrust, your lander will not be able to take off of the surface. However, if you go
just one thrust setting above your ideal thrust, you can make your lander take off.
10) Use what you know about the ideal thrust to control the lander to make a soft landing. Take a screen shot
of you making a “soft landing.”
(Paste screenshot here)
11) Try a similar simulation. Go to http://lander.dunnbypaul.net/ and show a successful land with a screenshot.
12) Go to http://www.coolmath-games.com/lunarlander/index.html or
http://www.squadron13.com/games/lunarlander/lunarlander.htm . Set the simulation to the “Earth setting” (see the
red arrow). Take a screen shot of you sitting on the furthest platform you can get to within the allotted class
time. Make sure it says “Landed Successfully.”
(Paste screenshot here)
EXTRA CREDIT: Using the PhET Lunar Lander, the person(s) with the highest landing velocity (crash) will
get EC points. Paste the screenshot.