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Newton’s Laws of Motion

See how we approach teaching Newton's Laws of motion using astronomy as the context.
Meet our astronauts, Bella, Isaac, Neeva, and Max. They’re about to go on a six month journey to Mars. In their training they learned three very useful laws for their mission. Newton’s three laws of motion. They describe how things move, and they allow us to predict the motion of an object over time. On their way to the rocket, they are very excited. Jumping feels natural to them. They know they will eventually stop mid-air and accelerate down to the earth under the force of gravity. They have a mass that will always remain the same, but their weight depends on the strength of the gravitational field they’re in.
In the spacecraft at the top of the rocket, the crew prepare for their life changing trip to another world. The fuel is ignited. As the gases are expelled and forced downwards, a force pushes the rocket upwards. This is Newton’s third law. The upward force on the rocket makes it accelerate. This is Newton’s second law. If the force was twice as strong, the acceleration would be twice as great. If the rocket was twice the mass, it would need twice the force to produce the same acceleration. The four astronauts experience their first strange symptom. They feel heavier. As the rocket detaches, the spacecraft enters space.
It is now moving at constant velocity because there is no overall force acting on it now the thrusters are turned off. This is Newton’s first law. The astronauts now feel weightless. They are constantly falling whilst in orbit around the Earth. After a long journey, Mars’s gravity pulls them in, and they accelerate. They move from Newton’s first law to the second law. Upon entering the Martian atmosphere, they release parachutes to decelerate the spacecraft. Small thrusters are ignited. The gas is expelled downwards, producing an upwards force on the spacecraft via the third law. The spacecraft decelerates, and they finally land on the surface.
As the team climb out into the cold harsh desert of Mars, they feel 60% lighter here compared to the Earth. They jump for joy, reaching higher than before, their movements forever determined by Newton’s laws.

Newton’s Laws of Motion are a fundamental set of laws that help us understand the action of forces and why things move in the way they do.

  • Newton’s First Law of Motion tell us that an object will carry on at the same speed and in the same direction (at the same velocity), unless a force acts upon it.
  • Newton’s Second Law of Motion states that when a force is exerted on any mass, that force will cause the mass to accelerate. The force applied is proportional to the acceleration, so if you double the force, the acceleration is also doubled.
  • Newton’s Third Law of Motion describes how when a force from one object is exerted on another, an equal (in size) and opposite (in direction) force acts back on the original object.


  • Mass – the amount of matter in an object, measured in kg.
  • Force – action which changes an object’s motion, size or shape.
  • Speed – rate of change of distance with respect to time.
  • Velocity – rate of change of distance with respect to time in a certain direction.
  • Acceleration – rate of change of velocity with respect to time.

Watch the video above to see how we introduce and teach Newton’s Laws of Motion, using the context of astronomy.

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Physics, Astronomy, and Space: Teaching Secondary Science

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