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Mechanics: Momentum, Energy and Gravitation

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

Why is the total momentum of an isolated system conserved, and how is this used to analyze collisions?

State the law of conservation of momentum, explain it using Newton's third law, and apply it to collisions and explosions where the total momentum before equals the total momentum after.
A Regents Physics answer on conservation of momentum: why total momentum is conserved in an isolated system, how Newton's third law explains it, and how to solve collision and explosion problems with total momentum before equal to total momentum after, with worked examples.
11 min answer →

What are the main forms of mechanical energy, and how does the conservation of energy let us solve motion problems?

Define kinetic energy, gravitational potential energy and elastic potential energy, and apply the conservation of energy to systems with and without friction, recognizing friction transfers mechanical energy to internal (thermal) energy.
A Regents Physics answer on mechanical energy and its conservation: kinetic energy, gravitational and elastic potential energy, the conservation of energy with and without friction, and how friction transfers energy to heat, using the Reference-Table equations, with worked examples.
12 min answer →

How is the momentum of an object defined, and how does a force acting over time change it?

Define momentum as $p = mv$ , define impulse as $F\Delta t$ , and apply the impulse-momentum relationship $F\Delta t = \Delta p$ to calculate force, time or change in momentum.
A Regents Physics answer on momentum and impulse: momentum as mass times velocity, impulse as force times time, and the impulse-momentum relationship from the Reference Tables, with applications to collisions and safety, plus worked examples.
11 min answer →

Why does an object moving in a circle at constant speed still accelerate, and what supplies the force?

Describe uniform circular motion, calculate centripetal acceleration with $a_c = v^2/r$ and centripetal force with $F_c = mv^2/r$ , and identify the real force that supplies the centripetal force in a given situation.
A Regents Physics answer on uniform circular motion: why circular motion is accelerated even at constant speed, how to calculate centripetal acceleration and force with the Reference-Table equations, and what real forces supply the centripetal force, with worked examples.
11 min answer →

How does the gravitational force between two masses depend on their masses and separation?

State Newton's law of universal gravitation, apply $F_g = Gm_1m_2/r^2$ to calculate the gravitational force, and use the inverse-square relationship to reason about how the force changes with distance.
A Regents Physics answer on universal gravitation: Newton's law of gravitation, the inverse-square dependence on distance, the meaning of the gravitational field strength, and how to apply the Reference-Table equation, with worked examples and proportional reasoning.
11 min answer →

When does a force do work, and what does power measure?

Define work as $W = Fd$ for a force along the displacement, relate work to the energy transferred, and define power as the rate of doing work, $P = W/t = Fv$ .
A Regents Physics answer on work and power: what work is and when a force does it, the link between work and energy transfer, and power as the rate of doing work, using the Reference-Table equations $W = Fd$ , $P = W/t$ and $P = Fv$ , with worked examples.
11 min answer →