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How can a rocket move when there is nothing to push against?

A swimmer pushes water backward and a car's tires push against the road. A rocket does not need surrounding air: it expels material, and the rocket and exhaust exchange momentum. Compare that process with two drifting astronauts pushing apart to explore what is conserved and where the energy comes from.

3–7 min

Questions you could explore

  • Why do a rocket and its exhaust not need equal speeds to conserve total momentum?
  • How can two drifting objects gain kinetic energy while their combined momentum remains unchanged?

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  • NASA Glenn Research CenterRocket Thrust

    NASA uses a rocket and its exhaust to explain reaction forces without surrounding air. The same momentum idea can be considered with two imagined drifting objects.

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Physics

Why metal can feel colder than wood

A metal handle and a wooden tabletop can share a room temperature yet feel quite different. The clue lies in the exchange of heat between your hand and the surface, which is not the same thing as measuring temperature.

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Why metal can feel colder than wood

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4–5 min

How can headphones fight noise with more sound?

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How can a ship made of steel float?

A solid piece of steel sinks, yet a steel ship can carry people and cargo. Its hollow shape changes how much water the whole vessel can push aside, making the material alone an incomplete explanation of floating.

3–5 min

How can a ship made of steel float?

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