#AP Physics 1: Momentum - The Night Before 🚀

Hey! Let's get you totally prepped for the AP Physics 1 exam. We're going to break down momentum, systems, and how it all connects. You've got this! 💪

#Systems: Open vs. Closed

Understanding systems is KEY for momentum problems. Let's clarify:

• Closed System: Think of it like a sealed box. No mass, energy, or charge can get in or out. Whatever's inside stays inside. 🔒

  • Key Point: Total momentum within a closed system is always conserved.

• Open System: Imagine a fish tank. Stuff can be exchanged with the outside world. Water, fish food, etc. can go in and out. 🐠

  • Key Point: Momentum is not necessarily conserved because the system can gain or lose momentum.

Image Credit: physics.usyd.edu

#Momentum of a System

Let's get into the nitty-gritty of momentum within a system:

• Internal Forces: These are forces within the system (like your hand pushing a cart). They always come in action-reaction pairs (Newton's 3rd Law).

  • Key Point: Internal forces always cancel each other out. They don't change the total momentum of the system. 💡

• External Forces: Forces acting on the system from outside (like friction or gravity). These do affect the total momentum.

• Net External Force and Momentum:

  • If the net external force is zero, the total momentum of the system is conserved. $p_{initial} = p_{final}$

  • If there is a net external force, the momentum of the system changes. $\Delta p = F_{net} \Delta t$