Catapult Project

Build a trebuchet that is capable of launching a large marshmallow from a distance of 3 to 5 meters, and hitting a target that is .30 m high +/- .10 m. You will have 5 trials to hit your target at each distance, and will be graded according to your building design, accuracy, and analysis.

The Trebuchet Page

Trebuchet Physics:  A Student View

Trebuchet Simulators

Trebuchet Experiments (needs Java)

Nova Builds a Trebuchet

Rubric and Questions for Analysis

(Print this part of the blog post and complete individually)

# hits at 3 m __________   # hits at 4 m__________ # hits at 5 m__________

Now, determine the velocity of the object using a video that shoots a cross-view of the projectile's motion.  This video must be uploaded to marciarpowell@gmail.com  You must analyze the video using logger pro before doing the analysis below.

1. Where is the biggest frictional issue in your machine?  Explain why this matters to the momentum of the mallow.
2. Determine the maximum range for your trebuchet, t(calc), and the initial values of v(x) and v(y) including a diagram  using logger pro
3. How could you determine F(net) of the mallow?
4. How will the momentum of the projectile change if we use jawbreakers instead of marshmallows?  An orange?  Why?
5. Pick a time frame for your catapult.   Determine the change in t, the acceleration due to gravity, and the distance traveled.  Based on this, calculate v(i) at the beginning of the interval and v(f) at the end of the interval in the x and the y directions.   Choose your interval carefully so you are not mixing y(up) and y(down)
6. Write a three to five paragraph summary of how you would change the design if you built another machine, and what you have learned about physics.  Include the following terms:  potential energy, kinetic energy, frictional force, net force, acceleration of gravity, vector errors, kinematic equations, independent x and y motions.

Evaluation for Seniors

Evaluation

GUILTY UNTIL PROVEN INNOCENT--a 2d momentum analysis

Guilty Until Proven Innocent

Problem:

How can you use the conservation of momentum to prove to a judge that you were not speeding and therefore do not deserve a ticket for the collision?

Materials:

Poster paper, protractor, ruler, calculator

Procedure:

You leave the school teacher's parking lot and are traveling north when you are broadsided by a car traveling east. The collision occurs in a school zone with a speed limit of 20 mph.  The impact throws you into the band practice field.

Following the collision the police officer determines that both vehicles had a speed of 22 mph (9.8 m/s). The driver of the other car is an adult and claims that you were speeding and consequently should receive a ticket. You are to prove your innocence by using the conservation of momentum.

Research:

What type of a vehicle were you driving?  What type of a vehicle was the other driver riding in?  Look again at the safety and the mass of these vehicles at the NHSTA site (http://www.safercar.gov  ).  Use the same vehicle you looked up earlier this week.

Your vehicle_______________           Mass or weight____________

Their vehicle_______________           Mass or weight____________

Decide on the units for your momentum and record here ____________

Draw a diagram of the two cars just prior to impact. You were headed north, the other car was headed East. Choose a scale (e.g., 1 cm = kg m/s) or freehand draw a diagram of the vehicles before AND after the impact your calculation .  

There are two possible cases.  In Case 1, you were going 20 mph.  In Case 2, they were going 20 mph.  One things for sure.  After the collision, you were stuck together and both of you traveled at 22 mph.

Do one set of calculations for each Case.

Summing Up (each person does this individually,1/2 to 1 page, and hands it in paper clipped to the diagrams)

1. Qualitatively explain, using your diagrams, how you know that you were not going faster than the adult. Remember that a ticket means higher insurance rates and a large fine.

2. Do you think you were you speeding?

3. How would angles affect your logic?

4. What evidence of impulse or guilt would the police collect in this action?
5.  Based on the safety rating of the vehicles involved, what do you think the extent of the injuries would be?

Using Video with Logger Pro

Video collection

Analyze before and after pictures for momentum for at least 3 of the data sets below.