Targeting A Sweet Spot

45 Minute Lesson

NJ Standards

5.2.12.E.1 – The motion of an object can be described by its position and velocity as functions of time and by its average speed and average acceleration during intervals of time.
5.1.12.D.2 – Science involves using language, both oral and written, as a tool for making thinking public.
5.1.12.D.1 – Science involves practicing productive social interactions with peers, such as partner talk, whole-group discussions, and small group work.

NJ Standard / Goal / Evidence /
5.2.12.E.1
5.2.2.E.2 / Students will be able to design a projectile launcher to launch short, mid and long range projectiles. / Students will be able to construct a catapult that can vary launching mechanism in order to launch a projectile a far distance.
5.1.12.D.1
5.1.12.D.2 / Students will be able to discuss engineering design principles related to the history and application of projectiles. / Students will be able to communicate about the significance of projectiles as well as contemporary and historical uses.

Resources

Student Use: Wooden Popsicle Sticks, Glue, Cardboard, Rubber bands, Cotton Balls, Spoons

Pre-Requisite Knowledge

  Translational Kinematics

Real World Applications

  Projectile Launchers Historical
Historical projectile launchers were commonly used in warfare as they were more powerful weapons. Arrows, cannons and other weapons are some examples.

  Projectile Launchers Contemporary
Machines have become more complex. Students should also be able to identify projectile launchers in our modern society including machines and even sports. Baseball and tennis machines are pacifistic projectile launchers and there are other

Potential Difficulties

  Students may not address realistic assumptions in building projectile launchers and may not be able to optimize launch angles for maximum projectile range.

  Students may have difficulties reinforcing their projectile launchers from self destruction upon launching.

  Students with difficulties in 2-dimensional kinematics may have difficulties in determining the maximum range for a projectile.

Lesson Description

  1. Opening (5 minutes)
    In the Ice Age where it is important to live while hunting giant animals what tools are most practical? Have students brainstorm ancient tools used for hunting.
    [Students should determine that projectiles are the safest tools. Alternatively sharp tools are most useful for hunting, however close range is not always practical]

B.  Building a Catapult (15 minutes)
Students will divide into groups and build their own projectile launcher. The stipulations are that the catapult must be a multi-use projectile launcher that can change projectile range. Have students identify the optimal configuration for maximum range theoretically and then find the experimental optimal configuration. Students should note any changes to their design in order to increase their range.

  1. History of Projectiles (15 minutes)
    Have students in groups build a flowchart for the evolution of projectiles. It may start from a rock and end at a missile. After the flowchart is produced, the class will convene and construct an all-encompassing flowchart. Groups will take turns identifying purposes for improvements, physics principles, and actual engineering designs to further projectiles. Students may determine that projectile engineering became much more complex over time if they consider hydraulics, steam powered devices, time release mechanisms etc.
    Students may come to the conclusion that a majority of projectiles are weapons, encourage students to come up with projectiles that are not weapons if there are too many weapons.

D.  Reflection (10 minutes)
Students reflect on why projectiles were developed, the physics of projectiles, and how projectiles evolved over time.

Time Table

Activity / Time Duration (Clock) / Students doing / Teacher doing /
A – Opening / 5 minutes (0:05) / Discussion / Discussion
B – Building a Solar Catapult / 15 minutes (0:20) / Building and testing / Presenting materials, Observing
C – History of Projectiles / 15 minutes (0:35) / Brainstorming, Presentation, Discussion / Discussion
D – Reflection / 10 minutes (0:45) / Reflection / Discussion

Formative Assessment

What is the optimum angle for the maximum projectile range? / Theoretically, a 45 degree angle attains a maximum projectile range. However, experimentally there are many assumptions that may make this error prone.
Students may find that elastic potential energy principles can be used by using rubber bands to build their launch mechanism. Alternatively, rubber bands need not be used if the spoon is secured such that it can be depressed.
Homework / Purpose /
Students will take their catapult design ideas and improve upon it theoretically with materials they can find at home. What materials will you use and how are they expected to improve the range of their design from class. / Students can think about using other resources to engineer better devices. They have to think about features of their device that can be improved by changing variables and identifying such variables.