Newtons laws
Core Vocabulary
Force: A push or a pull that can make an object move, stop, or change direction.
Acceleration: Any change in motion, including speeding up, slowing down, or turning.
Inertia: The natural tendency of an object to keep doing what it is already doing and resist any change in its motion.
Mass: How much matter or "stuff" is inside an object. Objects that are heavier have more mass.
Newton's First Law of Motion (The Law of Inertia)
Core Rule: An object at rest stays at rest, and an object in motion keeps moving at the same speed in a straight line, unless an outside force pushes or pulls it.
Balanced Forces: When forces acting on an object are equal in size and opposite in direction, they cancel out. The object stays completely still or keeps moving at the exact same speed.
Unbalanced Forces: When one force is stronger than the others, it causes an object to speed up, slow down, or change direction.
Car Example: When a car suddenly stops, your body lunges forward because your inertia wants to keep moving at the car's original speed.
Seat Belts: A seat belt provides the safe outside force needed to stop your body from moving forward.
Newton's Second Law of Motion (Force, Mass, and Acceleration)
Core Rule: How quickly an object speeds up depends on how heavy it is and how hard you push it ().
Mass Matters: Heavy objects with a lot of mass need a much bigger push to get moving or to stop compared to light objects.
Pushing Harder: The harder you kick or push something, the faster it will speed up.
Shopping Cart Example: An empty shopping cart is light and speeds up with an easy push, but a cart full of heavy groceries takes a lot more muscle to move.
Newton's Third Law of Motion (Action and Reaction)
Core Rule: For every action, there is an equal and opposite reaction. Whenever one object pushes on another, the second object pushes right back with the exact same strength in the opposite direction.
Forces Come in Pairs: Forces never work alone; they always happen in pairs.
Wall Example: When you lean your hands against a wall, you push on the wall, and the wall pushes back on your hands with the exact same amount of force.
Rocket Launch Example: Rocket engines blast hot gas downward (action), which pushes the rocket body straight up into space (reaction).
Motion in Space
Mass vs. Weight: Your mass is the amount of stuff you are made of, and it stays the same anywhere in the universe. Your weight changes depending on how hard gravity pulls on you. On the Moon, you would weigh much less because gravity is weaker, but your mass would stay identical.
Floating Astronauts: Astronauts float inside the International Space Station (ISS) because the station and everything inside it are falling around Earth together in constant free fall.
Circular Orbit: Earth's gravity continuously pulls on the ISS, bending its forward motion into a curved circle around the planet.
Straight Line Travel: If Earth's gravity suddenly vanished, inertia would make the ISS shoot off into deep space in a straight line.