Rocketry Basics

Principlesof Rocketry

How Newton's Laws Affect Our Rockets

The pressure inside the
rocket must overcome
the INERTIA of the
rocket’s weight to
launch. If the rocket has
too much water, it will
have too much
weight/INERTIA. THIS
IS WHY WE ONLY USE
1/3 BOTTLE OF
WATER.

Newton's First Law

An object will stay at rest
unless acted upon by a
force. An object will stay
in motion unless acted
upon by a force.

This is why you need just the right mass and
force to achieve a good acceleration.

40 psi is perfect for 300-400g

Force=Mass times acceleration

Newton's Second Law

Force is equal to mass
times acceleration

Isaac Newton's
3rd law of Motion

■For every action

■ there is an equal and

opposite reaction

What is the Action?
Solid Fuel Rockets

■Fuel in solid form burns and is converted to
hot gasses

■Hot gasses expand and create high pressure

■Pressure escapes out nozzle, pushing against
air and rocket body equally

- Reaction: Rocket moves forward, as

gasses move backwards

Newton's 3rd Law and Our
Water Rockets

■Instead of hot gasses creating pressure, we
use a bike pump and store pressure

Action: Expelling water from engine bottle.

(water is forced down)

Reaction: Water resisting against rocket
body.

(Rocket is forced up)

Reaction
Force:
Bottle
forced up
by water
being
expelled
down.

Action Force:
Water being
expelled down.

​15 PSI

​Newton's 3rd Law

​55 PSI

Stability During Flight

Center of Gravity

Center of Pressure

The orientation of fins and distribution
of mass help make the rocket stable.

Stability During Flight:
Think about a dart.

Fins or feathers
in the rear act
like wind veins
and keep it
stable.

Heavy mass in front carries the
momentum

More
mass in
the nose cone keeps the rocket stable. How could you add mass?

The orientation of
fins and
distribution of mass
help make the
rocket stable.

​Stability During
Flight

Newton's 3 Laws of Motion Explains

Everything

Newton's 3 Laws of Motion

• #1An object will stay at rest unless a force

acts upon it.

• #2Force = Mass x Acceleration

• #3For every action there is an equal and

opposite reaction.

The Rocket has no
Kinetic Energy
while on the launch
pad because it’s not
in motion or has no
velocity.

As the rocket gains
velocity, its Kinetic
energy increases.

At the peak of its flight,
friction and gravity have
overcome its momentum
and momentarily it’s
Kinetic Energy has been
converted into Potential
Energy.

As the rocket falls
back to earth, its
potential energy is
converted back into
Kinetic Energy as it
accelerates or
increases velocity.

Kinetic and Potential
Energy of Our Rockets.

Multiple Choice

Which statement best defines Newton's Third Law of Motion?

• An object at rest will stay at rest.

• The more mass there is the longer it will take to accelerate compared to an object with a smaller mass.

• An object in motion will stay in motion until a stronger, unbalanced force is acted upon the object.

• For every action there is an equal and opposite reaction.

Multiple Choice

Which best defines Newton's First Law of Motion?

• For every action there is an equal and opposite reaction.

• An object at rest stays at rest, or if in motion it will stay in motion.

• An object with a lighter mass will accelerate more compared to an object with a heavier mass.

• An object will remain motionless until it decides to move.

Multiple Choice

Newton's first Law of Motion is that an object at rest will stay at rest unless acted upon by an unbalanced force which also called the law of....

• force

• acceleration

• action and reaction

• Inertia

Multiple Choice

Newton's third Law of Motion is for every action there is an equal and opposite reaction which is called...

• Inertia

• Action and reaction

• Acceleration

• force

Multiple Choice

According to Newton's third law of motion for every reaction there is a (an)...

• equal and opposite reaction.

• force.

• acceleration.

• action.

Multiple Choice

According to Newton's second Law of Motion when a force is acted upon an object it will...

• stay at rest.

• loose mass.

• accelerate.

• gain mass.

Multiple Choice

Which statement shows the best example of inertia?

• A book lying on a table, the weight of the books is acting in the downward direction on the table

• An apple fell to the floor.

• The car hit a wall and stopped, but the girl still went forward.

• He rode the bicycle downhill.

Multiple Choice

Which example best represents Newton's third Law of Motion?

• A book lying on a table, the weight of the books is acting in the downward direction on the table.

• The car hit a wall and stopped, but the girl still went forward.

• He rode the bicycle downhill.

• An apple fell to the floor.

Multiple Choice

What example best represents Newton's 2nd Law of Motion?

• An apple fell to the floor.

• He rode the bicycle downhill.

• The car hit a wall and stopped, but the girl still went forward.

• The boy rode his bicycle downhill.

Multiple Choice

When you push on a wall, the wall pushes back on you with _____force.

• not enough

• more

• no

• equal

Multiple Choice

A rocket launches because of ______.

• its large mass
• an opposite reaction
• gravity
• air resistance