How does it work?
The motion of the bottle rocket illustrates Newton’s three laws of motion:
- The first law states that an object will remain at rest unless an unbalanced force acts upon it. In this case, the bottle rocket remains at rest on the launch pad until the force from the bicycle pump acts upon it.
- The second law illustrates the relationship between force, acceleration and mass. The amount of force pushing the rocket upwards depends on the volume of air pumped into the rocket. Adding a little more water increases the mass of the rocket, which then increases the action force applied as the water is expelled by
the air being pumped into the rocket. This causes the rocket to accelerate upwards faster.
- The third law states that for every action, there is an equal and opposite reaction. The action force created by the water and air being expelled downwards out of the bottle causes the reaction of the bottle being pushed upwards.
The four forces of flight are also acting upon the upward motion of the bottle rocket:
- Drag acts in the opposite direction of motion due to air resistance;
- Lift acts perpendicular to the direction of motion, helping to maintain stability and control the direction of flight;
- Thrust acts in the direction of motion pushing the rocket upwards; and
- Weight acts downward due to gravity.