Catapult Investigation - page 1
Keywords: Physics elastic spring stretch
By Jenny on 02/07/2009
Level: GCSE Key Stage 4 (Years 10-11)
Page Number: 1 of 3 pages: 1 2 3
Catapult Investigation
Introduction
When we stretch a spring or piece of elastic energy is stored in the spring or elastic. The more the elastic/spring stretches, the more force it contains. This is shown on the graph below.
The area under the graph (coloured blue) is equal to the energy stored in the elastic/spring.
Energy stored = Area underneath graph = force x extension
When the spring/elastic is released the strain energy stored in it is converted into kinetic (movement) energy. The further it is stretched, the more strain energy in the spring/elastic and the more kinetic energy there will be when it is released.
How a fired pellet travels.
While the kinetic energy is pushing the pellet forward gravitational energy is pulling it down.
Gravitational energy = m x g x h
m = mass
g = gravitational field strength = 10ms²
h = height
This affects how far the pellet travels.
I am going to investigate how far a paper pellet goes after being fired from a catapult, and how much the amount the catapult is pulled back affects the distance the pellet travels.
Prediction
I predict that the further back the elastic of the catapult is pulled the further the paper pellet will go. These two amounts (how far the elastic is pulled back and how far the pellet goes) will increase together in direct proportion to each other until the elastic of the catapult cant be pulled back any further. This will happen because the elastic contains strain energy when it is stretched and when it is released this is converted into kinetic energy which propels the paper pellet. The further back the elastic is pulled the more strain energy there is and so more kinetic energy is produced which propels the pellet further.
Fair Testing
To make sure that it is a fair test I will only change one factor during the experiment and I will make sure that all other factors that might influence the experiment remain the same. The factor that I will change is the amount the elastic is pulled back. The factors that I will keep the same are: the size and weight of the paper pellet, the catapult used, the place fired and person using the catapult.
List of Equipment
Catapult
Paper pellets (18)
Tape measure
Ruler
Long flat surface
Safety goggles
Diagram of Equipment
Method
1. Get all the equipment.
2. Put on the Safety Goggles.
3. Clear the surface.
4. Lay out the measuring tape from the starting point.
5. Place the catapult on the starting point (making sure
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