Structures - the catapult challenge

You will need some marshmallows, skewers, plastic spoons, elastic bands and masking tape.

For part two of this activity you will also need a protractor, hot glue gun, tape measure and A3 paper.
 
 

Constructing the catapult in a more durable manner will enable students to use it over and over again without needing to modify due to structural failure.

Step 1 . On an A3 paper mark out 60 degrees using a protractor and glue the three skewers to form the base of the pyramid.
You may glue straight onto the paper as this will give extra support to the base.
Step 2 Glue the sides
Step 3 Secure the apex using masking tape and then glue with hot glue.
Step 4 Turn the spoon upside down and glue the skewer on the handle as shown on the right.
Step 5 Secure the spoon with masking tape.
Step 6 Glue the catapult arm to one of the corners of the base, as shown on the right. As the hot glue is setting move the arm up and down so that it does not set firmly in place and is able to move up and down. Click to see how it is done.
Step 7 Connect the arm to the apex using an elastic band.

Now that the catapult is complete, its time to put it to good use.

You will need to measure the distance the marshmallow travels so a tape measure is needed.

Each group will need to graph the relationship between the length the elastic band is stretched and the distance travelled by the marshmallow. Repeat several times for greater accuracy.
Your teacher will provide a container, a known distance from your catapult, into which you will have to deliver the marshmallow. The distance of the container should be chosen so it is within the range of your elastic band. You will have to use your graph to calculate how far you will have to stretch the elastic band in order to catapult the marshmallow the distance the container is from the catapult. You will only be allowed two attempts so your data must be very accurate.
Distance marshmallow travelled (cm) Length elastic band was stretched. (cm)
   
   
   
   
   
   
   
 

Using the graph paper provided by your teacher construct an appropriate set of axis and draw a line-of-best-fit for the data in the table above.

Your graph must have:
- a heading
- clearly labelled axis with the units
- dependent variable on the y-axis
- independent variable on the x-axis
- all points accurately plotted
- the line of best fit properly drawn

Consider the picture on the right. It shows the catapult ready to fire.
a) What type of energy does the catapult possess?

b) When the student releases the arm is converted into

Consider the picture on the right. It shows the path of the marshmallow.

a) What type of energy does the marshmallow have at:

A

B

c)

The image on the right shows a time lapse of a marshmallow catapulted into a container. The camera takes a picture every second.

Looking at the image what can you say about the marshmallow's:

horizontal speed>

vertical speed.