Lab Handout: Energy and the Trebuchet Pre-Lab Questions Research the history and operation of a trebuchet—specifically how the trebuchet uses energy and gravity and how the lever makes the trebuchet more potent. Use the information you find to answer the questions, which will help you prepare for your energy experiment.

1. When a trebuchet counterweight is hoisted by soldiers, what form of energy istransferred into the machine as work?

2. What is the relationship between the mass of the counterweight and theamount of work done on the projectile?

3. Describe how lifting a counterweight is doing work using the formula W = Fd.

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4. What force must be overcome to lift the counterweight?

5. If the mass of the counterweight increases by adding more mass, how does the force required to lift the counterweight change?

6. How is the work done to hoist the counterweight related to the potential energy of the counterweight at its specified height?

7. If energy is conserved, describe the kinetic energy of the projectile in relation to the work in and the potential energy of the counterweight.

8. Provide a well-written hypothesis that can explore the function of the counterweight in a trebuchet.

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9. Identify the dependent and independent variables in your experiment.

10. Where is a safe place to use your trebuchet?

11. How will you determine the work done to the counterweight to hoist it to the catapulting lever?

12. How will you measure the distance the projectile flies?

13. How will you use the dependent variable and independent variable in your data table?

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14. What factors need to be kept consistent during the experiment?

15. Why is it important to do multiple trials for each different counterweight and then calculate the average?

Lab Questions Answer the following questions to help you understand your parachute and forces experiment.

Data Enter the masses of your three counterweights in Table 1. The masses must be in kilograms.

Measure the height difference of the counterweight between the upper and lower positions in the trebuchet. This is the distance (d) over which gravity must be overcome to lift the counterweight. Make sure you express the value in meters.

Record this value here:

Force can be calculated by multiplying the mass of the counterweight by its acceleration (F = ma). A falling weight has acceleration due to gravity (9.8m/s2). Calculate the force applied by each counterweight, and enter the values into Table 1.

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The work done by the falling counterweight can be calculated by the formula W = Fd. Use the distance value you calculated above and the force applied by each counterweight to determine the work done by each counterweight. Enter your values into Table 1.

Table 1: Counterweight Data Mass of

Counterweight (kg) Force Applied by

Falling Counterweight F = ma

Work Done by Falling Counterweight

W = Fd

Table 2: Trebuchet Projectile Test Data Mass of

Counterweight (kg) Distance Traveled by the

Projectile (m) Trial 1 Trial 2 Trial 3 Average

Experimental Report Complete the following sections to produce an organized lab report.

Statement of the Problem What question(s) are you trying to answer with your experiments?

Materials Make a list of all items that you used to construct your trebuchet.

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Procedure Write a paragraph that explains how you constructed your trebuchet, what you did in the lab, and exactly how you did it. Note: Your procedure should be written in a way that would allow another person to build a similar instrument and repeat the experiment.

Results In one paragraph, describe the results of your experiment. Remember to include the following information:

• summary data or observations• data tables• graphs

Conclusions Based on your results, state whether or not your original hypothesis was supported.

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Can a relationship be determined between the dependent and independent variables? Is it positive, negative, or neutral?

Describe the effect of the work done on the counterweight to the work done on the projectile.

Explain why your results should be considered accurate or inaccurate. If you think there are some inaccuracies, this is a good time to describe any problems or difficulties that arose during your experiment and what could be done to prevent them in future experiments.

Give your recommendations to improve the performance of the trebuchet or to improve the testing procedure to give better data.

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