1. Exploring our World through S.T.E.M.
Catapult
Exploring our World through S.T.E.M.

2. Catapult Has anyone ever seen or built a catapult?
What does a catapult look like?
Does anyone have an idea on how to build one out of Popsicle sticks and a wooden dowel?
What do catapults do?

4. Catapults
A catapult is a device used to throw or hurl a projectile a great distance without the aid of explosive devices—particularly various types of ancient and medieval siege engines
A projectile is any object projected into space (empty or not) by the exertion of a force.

5. The word 'Catapult' comes from the two Greek words "kata" (downward) and "pultos" (a small circular battle shield).[2] Katapultos was then taken to mean "shield piercer". Catapults were invented by the ancient Greeks.[3][4]

6. One of the problems with warfare throughout history was that enemies had the annoying habit of hiding behind fortifications. The solution: to find a way of beating down, piercing or otherwise destroying part of the wall so as to gain entry. Alternatively, it was equally important to be able to keep others intent on destroying your walls at bay. Enter the one armed throwing engine.

7. It is surprising how much energy they can store.
Catapults can launch things a fair distance to 1,000 feet (150 to 300 meters) is common.
It is surprising how much energy they can store.
The gears are important, because they create a winch.
The winch allows a person to put a great deal of energy into the catapult over a period of time.
Then all of the energy releases at once, throwing the projectile.
A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the "tension" of a rope or wire rope (also called "cable" or "wire cable").

8. Force The force of an object is determined by its mass multiplied by its acceleration. Force is measured in Newtons (N). Take-off speed The velocity of an object is the measure of its speed, defined as the distance travelled over a set period of time. Velocity is measured in meters per second. (m/s). The difference between velocity and speed is that velocity can be expressed as a negative numerical value, whereas you can’t get negative speed. Acceleration Acceleration of an object describes changes in its velocity. Acceleration is measured in meters per second (m/s). The force comes from energy stored in the twisted rope, which is very strong and slightly elastic. When you twist it, it stretches. When you let it go it untwists again. The maximum force the twisted rope can exert is approximately the same as the maximum tensile force it can stand. Twist it any more and it would break. In reality the rope would need to be capable of forces greater than those calculated here, as we’ve made a few assumptions within the calculations that would lead to greater stress.

11. http://video. nationalgeographic

13. Newton’s First Law of Motion
An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
This law is often called
"the law of inertia".

14. So how does a catapult work?
Newton's first law.
this relates to the catapult be it states that an object will continue to move until another force is acted upon it. This is displayed by the arm of the catapult and the ball that we launch. The catapults arm is stopped at the point we think will let the ball fly the farthest. The arm would have kept on moving had there not been a block of wood in the way to stop it. The ball would have just stayed at rest in the pocket had the arm not used energy/force to move it forward. The ball kept moving even though the arm stopped because of inertia, there wasn't enough force to keep the ball in the pocket. The ball would also fly for a much longer amount of time if there wasn't any gravity pulling it back down to Earth.

15. The Skater
What is the motion in this picture? What is the unbalanced force in this picture? What happened to the skater in this picture?

16. But why?
Newton's second law: This is shown because our catapult has a lot of mass to keep the whole thing in place when much force is used to launch the ball.
The acceleration of the ball depends on the mass of the ball and the force of the pull.
This is otherwise known as Newton's 2nd law of motion.

18. Newton’s second Law Acceleration is produced when a
force acts on a mass.
The greater the mass
(of the object being accelerated)
the greater the amount of force needed
(to accelerate the object).

20. Newton’s Second Law
If there is a net force on an object, the object accelerates.
Its acceleration is directly proportional to the net force
Its acceleration is inversely proportional to the object’s mass
Its acceleration is in the same direction as the net force.

21. “directly proportional” means:
If the net force doubles, the acceleration doubles.
If the net force triples, the acceleration triples.
If the net force is half as much, the acceleration is half as much.
Etc.

22. “inversely proportional” means:
If the object’s mass doubles, its acceleration will be half as much.
If the object’s mass triples, its acceleration will be one-third as much.
If the object’s mass is half as much, its acceleration doubles.
Etc.

23. What is “mass”? Mass measures the inertia of an object.
All objects made of matter have inertia - that is, they resist accelerations (Newton’s First Law), but some objects resist more than others.
Mass is a scalar quantity.
SI unit of mass is the kilogram (kg).

24. Newton’s third Law of motion
For every action there is an equal and opposite re-action.
What does this mean?
This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard.

25. The rocket's action is to push down on the ground with the force of its powerful engines, and the reaction is that the ground pushes the rocket upwards with an equal force.

26. What else…
Newton's third law: For every action that happens with the catapult there is an opposite and equal reaction. When the arm is drawn back, that was the reaction of our arm's strength pulling it back. When the rubber bands pull the arm forward, the arm is also pulling on the rubber bands. When gravity pulls down on the ball, the ball is also pulling up on the Earth.
Impulse: Impulse shows that a little time results in a big force with our catapult. We tried to make the arm swing the ball as fast as we can that way the distance is greater.
Force of gravity: With the catapult we had to make sure that the ball is launched at a correct angle to ensure that the ball would be able to go its furthest. This has to do with gravity. We want to make sure that when the ball is released that the ball doesn't just go straight towards the ground as a result of gravity. Gravity is going to pull on the ball the second its in the air by itself. This is how gravity affects the distance the ball will travel.

27. Catapult

28. Why a Catapult?
Catapults have been designed by engineers for a variety of purposes — from lifting boulders into the air for warfare to human beings for entertainment; the projectiles in this activity are grapes for a magic act. Given the building materials, students design and build their catapult to launch a grape a certain distance.

29. Catapults and engineering
Use the engineering design process to create a compound machine - the catapult.
Describe the interrelationship of the simple machines within a compound machine.
Describe the constraints of their model in the context of engineering

30. A catapult is a compound machine
Compound machines are two or more simple machines interacting with one another to do work. We can find them all around us in everyday items, including a can opener, a pencil sharpener, a wheelbarrow, a pair of scissors and a piano. Compound machines are dependant on each of its simple machines. If just one of the simple machines in a compound machine is removed, the compound machine will not function nearly as well. Engineers use their knowledge of simple machines to create many of the compound machines we use every day.

32. Step 1
Good engineering is characterized by well thought-out designs that are also attractive.
An unnecessary amount of building material, such as glue, is not attractive and is considered wasteful. Just a daub of hot glue on each connection should suffice.
Hot glue dries quickly and becomes quite strong.
connect
Build each upright and connect the two pieces together as shown in Figure.

33. Tie a rubber band to the stick that connects the two uprights as shown in Figure, leaving a loop extending upwards.
The tension
Tension is a force related to the stretching of an object (the opposite of compression)

34. Cut a short piece of straw and slide over wooden dowel.
Attach wooden dowel across top of side braces with two daubs of glue.
Glue rubber band to tongue depressor and the tongue depressor to the straw, as shown in Figure 4. Horizontal braces should be added to stiffen the structure.
To produce the force
Force, a push or pull that can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or which can cause a flexible object to deform

35. The tongue depressor, which is the arm of the catapult, should rotate freely about the dowel allowing for the tension in the rubber band to be felt. See the Figure.
Rotation
A rotation is simply a progressive radial orientation to a common point. That common point lies within the axis of that motion.

36. Finish the catapult with a portion of straw glued to the arm to keep the grape in place. Also add two more sticks to the front (left side, see Figure 6) of the catapult to stabilize it after launch.
stabilize
Front and rear stabilizers keep catapult from flipping. A straw is added to the end of the tongue depressor to prevent the grapes from sliding off during launch

37. Now let’s see

38. Check your design
how can you improve the catapults?
sketch your ideas