Catapult Science

What is catapult science? How can you make your catapult shoot further?

Well, to do that we need to understand some of the science behind what happens when it shoots an object (like a pebble)!

When the catapult shoots an object, it gives it both a vertical speed and a horizontal speed. How much of each depends on the angle the catapult shoots from. If the catapult tilts straight up, all the speed is in the vertical direction, the pebble does not go very far (just high). If the catapult tilts perfectly sideways, gravity (g) will pull the pebble to the ground too quickly!

To shoot a far distance (sideways) you need to the pebble sideways and up. By doing this, you give the pebble some time to hit the ground while still moving sideways (so it can travel a longer distance):

catapult science flight path

You can adjust the Shooting Angle by placing the catapult on a small notebook and adjusting the tilt (see picture below):

ideal shooting angle for catapults

The second thing that affects how far the catapult shoots is the shooting speed. This can also be adjusted by tightening of loosening the rubber band.

So, how does the shooting speed and angle affect the distance that the catapult can shoot? Try a few different angles and tensions in the rubber band and see if you can notice any effect.  If you make the rubber band tighter, do you increase the shooting speed? What does that do to the shooting range?

Advanced:

What if you make the shooting angle larger of smaller? What is the best shooting angle?

Using Physics and Mathematics you can estimate the distance the catapult can shoot.  If you have experience in these topics you can go here to see how the equations are formed.

If not, that’s okay!  We’ll just put the final equation here:

In the equation there are four variables, each representing something.The range r is how far the catapult shoots. This is what you want to know. The shooting speed v is related to how tight your rubber band is (tighter increases the shooting speed). The gravity g is something that is called a constant – we assume it does not change. Last, the shooting angle (theta) is how much you tilt the catapult when shooting.

The sine (sin) is a special function that changes value depending on the angle. All you need to know is that it is a maximum when 2*theta is equal to 90 degrees (or theta is 45 degrees, halfway between completely vertical and flat).

So, looking at the equation what can you find out? Well, two things: First, increasing the rubber band tension increases the speed, which increases the range. Second, the shooting angle should be at 45 degrees for maximum range.

Now that you know these pieces of knowledge play with your catapult some more. See if you can modify the design for maximum range.  How far can you shoot?  Tell us!!

24 Responses to “Catapult Science”

  1. William Jelbert May 21, 2012 at 5:11 am #

    Say whaaaaaat…?

  2. Warren October 16, 2012 at 1:27 am #

    MY son would like to cite this article in a research project. Can you give us more info?

    • Jules December 8, 2013 at 9:15 pm #

      I need to cite this too

    • tromoty September 27, 2016 at 9:23 pm #

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  3. your mom October 24, 2012 at 12:36 pm #

    yah mom

    • Tony September 21, 2016 at 4:38 pm #

      Yo dad bitch

  4. ben dsy October 31, 2012 at 2:16 am #

    #lol

  5. angie August 27, 2013 at 10:19 pm #

    thanx, it was a huge help for a class project!

  6. allyson September 5, 2013 at 7:17 pm #

    hey thanks for this. im doing a science fair project on does the length of the catapult affect the rock distance and speed. so thanks for some research

  7. josh goeargfe October 10, 2013 at 6:01 pm #

    hi

  8. meow February 11, 2014 at 10:14 pm #

    Thanks for the info

  9. lolman December 7, 2015 at 7:23 pm #

    nice info

  10. milhaan January 17, 2016 at 10:15 am #

    Hi, that’s nice. So considering the G to be a constant value, that will be the same. So if your increase your rubber band speed (v) then that ( v x v ) is directly proportional to the distance(but divided by the g constant though). So for this(distance) to be directly proportional to the square of the speed , there is one other factor , the value of sin(2theta) , so the max value can be 1, sin(2theta) = 1). so what ever speed (v) multiplied by this 1 will be the speed itself! and if multiplied by less than 1 then it is decrease in speed!. The max value of working with the sin (theta) is 1. so if you shoot at 45 degress , then the only decelerating force acting on the projectile will be the gravity! But you know there is also some other guy! guess what the air friction!!!

  11. Gnarly Gnarly March 23, 2016 at 11:42 am #

    Gnarly

  12. Dank Memes May 9, 2016 at 7:05 pm #

    Dank Bro

  13. Katie and Emily May 12, 2016 at 3:31 pm #

    thanks we really needed this info!

  14. Kyle June 6, 2016 at 9:28 pm #

    45 degree isn’t the ideal angle when making a catapult as lower the angle, lower the acceleration the object gains while reaching to its departing point. You need some mathematics to find optimal one it is certainly between 45 to 90degrees

  15. Alpha September 14, 2016 at 12:33 am #

    A catapult is a cool design, I’ve made heaps of them.

  16. Alpha September 14, 2016 at 12:34 am #

    A simple class 3 lever is a good start.

  17. SmartAlic September 22, 2016 at 2:47 pm #

    I understand

  18. Christian September 28, 2016 at 5:23 pm #

    all hail lord beanbag

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