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What is a closed system?
A system where no mass, energy, or charge can enter or leave.
What is an open system?
A system that can exchange mass, energy, or charge with its surroundings.
Define momentum.
Momentum ($p$) is the product of an object's mass ($m$) and velocity ($v$): $p = mv$.
What are internal forces?
Forces acting within a system that always come in action-reaction pairs and do not change the total momentum of the system.
What are external forces?
Forces acting on a system from outside that can change the total momentum of the system.
Define Impulse.
The change in momentum of an object. Impulse ($J$) is equal to the net force ($F$) acting on an object multiplied by the time interval ($\Delta t$) over which it acts: $J = F\Delta t = \Delta p$.
What is the key difference between open and closed systems regarding momentum?
Closed System: Total momentum is always conserved. Open System: Momentum is not necessarily conserved.
Differentiate between internal and external forces in a system.
Internal Forces: Act within the system, cancel each other out, and don't change total momentum. External Forces: Act on the system from outside and can change total momentum.
Compare momentum and kinetic energy.
Momentum: A vector quantity, always conserved in a closed system. Kinetic Energy: A scalar quantity, not always conserved (e.g., inelastic collisions).
What is the difference between elastic and inelastic collisions regarding kinetic energy?
Elastic Collision: Kinetic energy is conserved. Inelastic Collision: Kinetic energy is not conserved; some energy is converted to other forms (e.g., heat, sound).
Compare and contrast the effects of internal and external forces on the momentum of a system.
Internal forces do not affect the total momentum of a system, as they cancel each other out. External forces directly change the total momentum of a system.
What happens to the total momentum of a closed system if no external forces act on it?
The total momentum remains constant (is conserved).
What is the effect of a net external force acting on a system?
The momentum of the system changes. The change in momentum is equal to the impulse applied to the system: $\Delta p = F_{net} \Delta t$.
What happens when a rocket expels hot gas?
The rocket moves forward due to the conservation of momentum. The momentum of the gas expelled in one direction is equal and opposite to the momentum gained by the rocket.
What is the effect of friction on the momentum of a system?
Friction, as an external force, causes the momentum of the system to decrease over time.
What happens to the kinetic energy of a system during an inelastic collision?
Kinetic energy is not conserved; some of it is converted into other forms of energy, such as heat or sound.
What happens when two objects collide and stick together?
The objects move together as one mass, and the total momentum of the system is conserved (assuming no external forces).