Kia Ora
In Science we have been making bottle rockets.
Aim: To make a successful bottle rocket and investigate forces.
Equipment: Plastic container, foil tape, normal tape, two plastic bottles, plastic half cylinder and hot glue.
Method:
- Cut out 3 fins from a plastic container.
- Cut the second bottle in half.
- With hot glue and foil tape, tape the second half bottle to the first whole bottle.
- Hot glue the fins onto the combined bottles so they are an equal distance apart.
- Tape the half cylinder to the top of the half bottle that was taped to another bottle.
Results:
These are the results for all of the rockets flown:
| Distance travelled (m) | Time taken (s) | Speed calculation (ms-1) |
| 52.10
24.80 13.40 18 46.50 14.40 |
3.72
1.69 2.93 2.32 2.28 1.66 |
14.01
14.67 4.57 7.76 20.39 8.67 |
My groups rocket flew 52.10 m and took 3.72 s, so its speed was 14.01 ms-1 or m/s (52.10/3.72 = 14.01)
Discussion:
- What are the forces acting on your bottle rocket?
- The forces acting on the bottle rocket is lift, thrust, gravitational and air resistance.
- Are they balanced/unbalanced?
- The forces acting on the bottle rocket are unbalanced, because the rocket is moving forward and going up. The gravitational and air resistance forces are not as strong as lift and thrust, so the forces of the bottle rocket are unbalanced.
- What is net force and how does this relate to the forces acting on your bottle rocket?
- Net force is the total force acting on an object. This relates to the forces acting on the bottle rocket because the forces are different and unbalanced, so the net force is the total force that is acting on the bottle rocket.
- What are the strength of forces acting on it at different stages?
- The strength of the forces acting on the bottle rocket is that the thrust is very strong since the rocket is moving forward, and the gravitational force is stronger when it goes down. When the rocket launches the thrust is very strong and gravitational is not as strong.
- How do the forces acting on the bottle rocket affect the motion of the bottle rocket at different points?
- The forces acting on the bottle rocket affect the motion of the bottle rocket at different points, because at the start when it launches, the forces acting on the rocket are different, the gravitational force becomes stronger than lift and pulls the rocket down. The air resistance is not as strong as thrust so the rocket moves forward. When the rocket hits the ground, gravitational force is the strongest as it is keeping the rocket on the ground, and lift is not as strong.
- Why do you think results may vary in the class?
- I think the results may vary in the class because people designed their rockets differently, so their rocket might not fly as well as others because the design is different. For example, if the rocket had no nose at the tip, there would be more air resistance for the rocket and it wouldn’t fly as well. If the rocket had a nose, there would be less air resistance and it would fly much better.
Forces acting on the bottle rocket:
Conclusion:
- How was your bottle rocket successful/unsuccessful and why (relate your answer to physics ideas)?
- The bottle rocket was successful because it launched well and flew through the air really well. The thrust of the rocket was really strong and there wasn’t much air resistance, so it flew quite far and had a good speed. The fins helped the rocket to fly too because they helped to keep it stable in the air.
- How could you improve it?
- We could improve the bottle rocket by adding more weight to the tip and adding more hot glue to the fins so they stay on the bottle. If we add more weight to the tip, it will keep it stable in the air.