9709 · 4.4
Newton's laws of motion flashcards
Revision flashcards for Cambridge 9709 Newton's laws of motion (syllabus 4.4). Flip, recall, then mark a real past-paper question.
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What is Newton's First Law of Motion?
An object will remain at rest or continue to move with constant velocity unless acted upon by a resultant external force. This is also known as the law of inertia.
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What is the formula for Newton's Second Law?
Resultant Force = Mass × Acceleration, or $F_{net} = ma$. The force must be in Newtons (N), mass in kilograms (kg), and acceleration in metres per second squared (m s⁻²).
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What is Newton's Third Law of Motion?
For every action, there is an equal and opposite reaction. The two forces in an action-reaction pair are of the same type, equal in magnitude, opposite in direction, and act on different bodies.
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What is meant by 'equilibrium' in mechanics?
An object is in equilibrium if the resultant force acting on it is zero. This means it is either at rest or moving with a constant velocity.
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What is the difference between mass and weight?
Mass is the amount of matter in an object (a scalar, measured in kg). Weight is the force of gravity acting on that mass (a vector, measured in N). Weight = mass × g.
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A book rests on a table. Are its weight and the normal reaction from the table an action-reaction pair?
No. They are both forces acting on the same object (the book). The reaction to the book's weight (Earth's pull on book) is the book's gravitational pull on the Earth.
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What is a 'resultant force'?
The vector sum of all the individual forces acting on a single object. It's the single force that would have the same effect as all the original forces combined.
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What are the standard units for force, mass, and acceleration in SI units?
Force: Newton (N), which is a kg m s⁻². Mass: kilogram (kg). Acceleration: metres per second squared (m s⁻²).
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What is 'Tension'?
The pulling force transmitted through a string, rope, cable or chain. It is assumed to act equally at all points along a light, inextensible string.
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When modelling connected particles, what is true about the tension in the connecting string?
For a single light, inextensible string passing over a smooth pulley, the tension is the same on both sides of the pulley.