Newton's 1st Law of Motion
- Every object remains in a state of constant velocity or remains stationary unless a resultant force acts upon it.
- A resultant force is needed to produce an accleration.
- If the resultant force is zero/no resultant force, the object will continue to move at a constant velocity/remain stationary.
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Newton's 2nd Law of Motion
- Resultant force = mass x acceleration
- Acceleration and force are vectors
- Resultant force is proportional to acceleration (and moves in the same direction)
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Newton's 3rd Law of Motion
- Every action has an equal and opposite reaction
- If body A exerts a force on body B, then body B exerts an equal and opposite in direction reaction force of the same type on body A.
- They are equal in magnitude, force type, and the time and line of action is the same.
- They act in opposite directions and on different bodies.
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- GRAVITY IS NOT A FORCE - it is acceleration
- Weight = downwards force
- Weight = mass x gravity
- Magnitude of acceleration in freefall = gravitational field strength
- Centre of gravity = the point where all the weight of an object is concentrated
(it is usually in the centre of the object)
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- A free body diagram shows all the forces acting on one object (at the centre of gravity)
- Weight always acts directly down
- Normal contact force (reaction force) acts perpendicular to the surface (ground/slope)
- Friction/drag forces always oppose motion.
- TENSION IS A FORCE
- Vector diagram = closed polygon if the forces are in equilibrium (resultant force = 0)
- Forces in equilibrium = constant velocity/stationary state (N1)
- Draw vector arrows from tip to tail (resultant vector = tail of first --> tip of last)
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