Watching a rocket propel itself into space is one of the most exciting things to see. But did you ever wonder what makes it go?
Well, yes, fuel of course. But fuel is only pushing against the ground. Why does the rocket move in the opposite direction, up?
You might have heard this famous phrase before:
"For every action, there is an equal and opposite reaction."
That’s from Isaac Newton’s Third Law of Motion. This law helps us to predict how things will move.
Wanna test this yourself? Let’s make a balloon rocket!
You may also want a friend or parent to help as your lab partner!
What's going on?
When you let go of the balloon, the air inside rushed out creating a force called thrust. Since the balloon is so light, the air is enough to propel (or push) the balloon forward.
For every action, there is an equal and opposite reaction:
Physicists call the air that came out of the balloon the ‘action force’ and the force that pushed the balloon forward the ‘reaction force’. When an action force goes in one direction, the reaction force goes in the opposite direction. The bigger the action force, the bigger the reaction force. This is why the balloon with most air in it went the farthest!
With real rockets, thrust comes from the force of burning rocket fuel as it blasts from the rockets engine. As the engines blast down, the rocket goes up! Just as Newton predicted: “For every action there is an equal and opposite reaction.” In other words, when you push on something, it pushes back on you just as hard!
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