Rockets and Newton's laws

Up, up and away

What we are going to achieve today

Understand Newton’s second and third lawsUnderstand how a rocket travels using an

action reaction force.Be able to use the formula; Force = Mass x

Acceleration.Create your own rocket that uses a

reactionary force.Use Newton’s Laws to explain why three types

of rocket travel at different speeds.

Big Questions!

How does a rocket get off the ground?

Why is a rocket shaped like a rocket?

Newton's 3rd law….

Every force has an equal and opposite reaction that acts on a different body, so the force produced from the water coming out of the bottle, pushes the bottle in the opposite direction.

A force cannot exist on its own – there is always a second force acting against it.

Newton’s third law

These pairs of forces that act between two objects are sometimes called action–reaction pairs.

If object A exerts a force on object B, then object B exerts an equal but opposite force on object A.

What happens when the rocket is accelerating, are the forces balanced or

unbalanced?

If an object is accelerating, the forces on it must be UNBALANCED.

If the resultant force acting on an object is not zero, all the forces are said to be unbalanced.

What is Newton’s second law?

the speed of the object may change – it may either increase or decrease

the direction of motion may change.

Rail Road Toffee Rocket

When are the forces balanced?Where are the forces unbalanced?How is the rocket car pushed forward?

How is movement calculated from force?The resultant force acting on an object is related to the object’s mass and acceleration. These three factors are linked by the following equation:

Resultant force is measured in newtons (N).

Mass is measured in kilograms (kg).

Acceleration is measured in metres per second per second (m/s2).

force = mass x acceleration

Using a formula triangle

F

M A

Task

• Complete F=ma questions

Newton’s 2nd Law

•What is the force on a 5kg mass accelerating at 2m/s/s?•What is the force on a 25kg mass accelerating at 0.25m/s/s?•What is the acceleration when a force of 20N is exerted on a 3kg mass?•What is the acceleration when a force of 45.6N is exerted on a 3kg mass?•What is the mass when a force of 60N makes something accelerate at 0.25m/s/s?

Balloon Rockets

The challenge is to make your rocket go the

furthest; the speed of the rocket is not relevant.

What is the best way to control the thrust?What is the best way to balance your rocket?

How does the mass of the particles affect the thrust?

• You have seen a water rocket, made an air balloon rocket and seen a real rocket launch!

• Can you explain the reason why these different methods create different amount of thrust?

• Remember F = ma• Every action has an equal and opposite reaction.• Think about the force on the particles.