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Grade 7


Module 4

Finding the rocket’s centre of gravity

Assignment 1:

How to find your rocket’s centre of gravity

[lo 1.14]

Make a loop at the end of a 1 m piece of string.

  • Tie the loop around the body section of your rocket.
  • Let the rocket hang free in your hand and shift the loop until the rocket hangslevel/parallel to the ground.
  • Indicate the centre of gravity on the rocket by drawing a line right around the body with a marking-pen. Indicate the symbol for centre of gravity.


The aerodynamic forces at a rocket’s centre of pressure are centred. The centre of pressure is usually also close to the tail end of the rocket. The large surface of the fins and the smooth surface of the rest of the rocket cause it to be the position where the pressure is the same on both sides. To get the centre of pressure closer to the tail of the rocket, the front section (nose) of the rocket has a more pointed shape or the body section of the rocket could be made longer, because in that way it becomes more aerodynamic. By putting smaller fins on the front section of the rocket, the centre of pressure is moved closer to the front end.

R ules : The centre of gravity should be closer to the front end of the rocket than the centre of pressure. The centre of pressure should be the same distance or longer than the diameter of the rocket from the centre of gravity to the tail end. This will make the rocket stable and will help it to fly in a straight line.

Assignment 2:

How to find a rocket’s centre of pressure

[lo 1.14]

Make a sketch of the side elevation of your rocket. Sketch the fins as well and draw as accurately as possible.

  • The centre of pressure is determined by drawing a line that spreads the surface of the rocket equally on both sides of the line.
  • Indicate the centre of pressure in the sketch by drawing a line through it.
  • Indicate the centre of pressure on the rocket by drawing a line right around the body with a marking-pen. Indicate the symbol for the centre of pressure.

Assignment 3:

Testing whether your rocket is stable during flight

[lo 1.13]

  • Make a loop at the end of a 2 m piece of string.
  • Tie the loop around your rocket at its centre of gravity. Affix the loop with adhesive tape if necessary.
  • The rocket should hang parallel to the ground surface (Sketch 1). Swing it around with a circular movement (Sketch 2).
  • Change the centre of gravity or the centre of pressure until your rocket swings forward in a straight line while hanging horizontally.

If you want to make any changes to your rocket to make it more stable, you can do it now. Decorate the bottles and fins so that it looks more like a rocket, for instance by painting it with an oil-based paint.

Now you are ready to launch your rocket.


Learning outcomes(LOs)
LO 1
Technological processes and skillsThe learner will be able to apply technological processes and skills ethically and responsibly using appropriate information and communication technology.
Assessment standards(ASs)
We know this when the learner:
Evaluates :1.12 evaluates the product or system based on criteria linked directly to the design brief and some of the specifications and constraints, and suggests improvements or modifications;
1.13 evaluates the efficiency of the plan of action followed and suggests improving future plans;
Communicates :1.14 presents ideas (in a project portfolio) using two-dimensional or three-dimensional sketches, circuit diagrams or system diagrams.


Assignment 1 - 3

Learners can help each other to find the centre of pressure and centre of gravity of every rocket. They will differ seeing that the appearance of each rocket should differ.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Technology grade 7. OpenStax CNX. Sep 10, 2009 Download for free at http://cnx.org/content/col11032/1.1
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