9702 · 3.1
Momentum and Newton's laws of motion flashcards
Revision flashcards for Cambridge 9702 Momentum and Newton's laws of motion (syllabus 3.1). Flip, recall, then mark a real past-paper question.
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What is the fundamental definition and formula for momentum?
Momentum ($p$) is the product of an object's mass ($m$) and its velocity ($v$); $p = mv$.
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State Newton's Third Law of Motion.
For every action, there is an equal and opposite reaction force, with these forces always acting on *different* objects.
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What is the key difference between elastic and inelastic collisions regarding energy?
In elastic collisions, kinetic energy is conserved; in inelastic collisions, it is not (some is converted to other forms).
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How does Newton's Second Law relate force to the change in momentum?
The net force is equal to the rate of change of momentum ($F_{net} = \frac{\Delta p}{\Delta t}$).
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What condition must be met for an object to reach terminal velocity?
The net force acting on the object must be zero, meaning all downward driving forces are balanced by upward resistive forces.
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What is another name for Newton's First Law?
The Law of Inertia.
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What are the standard units of momentum?
Kilogram-metre per second (kg m/s) or Newton-second (Ns).
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What does the principle of conservation of momentum state?
For a closed system, the total momentum before an interaction equals the total momentum after, if no external resultant force acts.
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How does mass differ from weight?
Mass is a scalar measure of inertia; weight is the gravitational force (W=mg), a vector, acting on an object.
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What characterises relative speed in a perfectly elastic collision?
The relative speed of approach before impact equals the relative speed of separation after impact.
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What is impulse and how is it calculated?
Impulse is the change in momentum of an object. It is also the product of the average net force acting on the object and the time interval over which the force acts. Formula: Impulse = FΔt = Δp.
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In the context of momentum, what is a 'closed system'?
A closed system is one where no matter is exchanged with the surroundings and no external resultant force acts upon it. This is the condition required for the total momentum of the system to be conserved.
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When is F=ma an incomplete form of Newton's Second Law?
F=ma is a special case that applies only when the mass of the object is constant. The more general form, F = Δp/Δt, is always true and accounts for systems where mass can change, such as a rocket expelling fuel.