Group+5+SUM13

Sacha, Thanh-Thuy

[|Lesson plan for catapult]

Video examples

How to build a catapult

Student activity worksheet(s) Backyard Ballistics Teachers Guide

Lesson Plan: Catapult Physics Objective: This lesson plan combines history and physical science. The objective is to apply Hooke’s Law and to show that science, history, and culture are closely interrelated and impact each other. Understanding history helps the comprehension of science and vice versa. Concepts: Catapult Taxonomy

Catapults are machines that were used by ancient civilizations to hurl projectiles in battles. Sometimes catapults are referred to as “ancient artillery”. There are four types of catapults, categorized by how they are powered. > bow from a bow and arrow) or elastic band (like a spear gun) to throw a rock or bolt. > person or group of people to throw a large rock.  > human muscles. > Hooke’s Law > > The amount of force stored applied to a suddenly released projectile from a spring is a linear function directly related to how far the spring is twisted or deflected. This is called Hooke’s Law and is: > Equation 1: Force = K x ∆, where K is the spring constant unique to the spring’s material > ∆ is the deflection of the spring. > This equation tells us that distance to which a catapult will shoot its projectile is directly proportional to the number of twists in the rope coil spring for a torsion catapult and is directly proportional to how far the bow is flexed in a tension catapult    Catapult Physics Page 1 of 2  Backyard Ballistics Lesson Plans Copyrighted material 2003  Field Work  We will use Hooke’s law to determine the spring constant in a torsion powered catapult. Build table top model catapult in accordance with the instructions found in chapter 5 of the book Backyard Ballistics by William Gurstelle (Chicago Review Press, 2001).
 * Torsion Catapults use the energy stored in a twisted rope coil to turn a throwing arm.
 * Tension Catapults use the energy contained in the fibers of a bent flat spring (like a
 * Traction Catapults are human powered. They generally used leverage to allow a
 * Gravity powered Catapults also use leverage, but substitute a heavy weight for

Other materials required, besides those listed in chapter five of Backyard Ballistics: To determine the spring constant (K) > the catapult. Walnuts make good projectiles. Fire the walnut five times. Measure and > record the distance the projectile is shot. > record the distance the projectile is shot. > centimeters on X axis and the number of twists in the rope spring on the Y axis. Questions: > curved line shows a higher order relationship. > relationship (Hint: the number of twists in a rope is not exactly the same as a simple > linear spring deflection) > devices may be built on a very large scale)  All rights reserved. William Gurstelle 2003. This document may be reproduced with the following stipulations: It must be used unaltered and in whole. It may not used commercially or on electronic or Internet related sites without permission. Users of this information are wholly and completely responsible for their own safety. No guarantee of safety is given or implied Contact: info@backyard-ballistics.com  Backyard Ballistics ( ISBN: 1556523750) is available from most bookstores, online, and from the publisher Sales: orders@ipgbook.com  Catapult Physics Page 2 of 2
 * 1) Tape measure
 * 2) Graph paper
 * 1)  Set up the catapult and count and record the number of twists in the rope spring. Fire
 * 1)  Tighten the rope spring a few turns. Fire the walnut five times and measure and
 * 1) Repeat step 2 two or three more times.
 * 2)  Graph the average results on the graph paper, plotting distance in inches or
 * 1) The slope of the line represents the spring constant for the rope spring.
 * 1)  Is the plotted line straight or curved? A straight line shows a linear relationship and a
 * 1)  If the line is curved how do you account for that, since Hooke’s Law is a linear
 * 1)  Which type of catapult could be built on the largest scale? (Hint: Gravity powered