unit 5: Momentum
Overview
Momentum is a vector quantity for "mass in motion"
p = mv
Momentum is a vector quantity for "mass in motion"
p = mv
- p = momentum
- m = mass (scalar)
- v = velocity
Impulse
- A force that is applied over time
- The change in momentum of an object
- Impulse can be a negative force or a positive force
- Ex. friction force, gravitational force, applied force
- J = F* Δt = Favg * Δt
- Isolated System
- Universe is the system
- J = 0
- Pi = Pf
- Nonisolated system
- Universe is not the system
- J = F * Δt
- Pi + J = Pf
- Time v. Force graph
- Area under the force is the impulse
- Impulse is also the average force times the total time
Conservation of Momentum
- LIL Chart
- Section for Initial Momentum, Impulse, and Final Momentum
- Above x-axis = momentum in positive direction
- Above y-axis = momentum in negative direction
- Pi + J = Pf
- Initial Momentum plus Impulse is equal to Final Momentum
- If no impulse, Initial Momentum = Final Momentum
Relating Momentum Energy, Forces, and Kinematics
Momentum <--> Energy
Momentum <--> Forces
Momentum <--> Kinematics
Momentum <--> Energy
- J = F * Δt
- given the change in momentum (J) over time, we can determine the net force
- We can plug this force into the work equation to determine the work done in a system
- W = F * Δx
- Ek = 1/2 * m * v^2
- Given the change in kinetic energy and mass we can find the velocity, which can be used to solve for momentum wit p = mv
- Eg = m * g * h
- Eel = 1/2 * k * Δx^2
Momentum <--> Forces
- We not the different forces involved to determine what the Net Force is when solving for Impulse J = F * Δt
- Normal Force = two surfaces in contact preventing each other from passing through (against Fg)
- Spring Force = force of a compressed string with object attached (opposite direction of compression)
- Friction Force = resistive force when an object rubs against another surface (force in opposite direction the object is traveling in)
- Applied Force = push or pull on an object (force in the direction the object moves)
- Tension Force = force transmitted by a rope, cable, or wire (force in the direction of the rope)
Momentum <--> Kinematics
- p = mv
- m is mass
- v is velocity
- p is momentum
- Given mass and velocity we can find momentum
- Vf^2 = Vi^2 + 2 * a * Δx
- a is acceleration
- Δx is change in distance
- Given momentum and mass, we can solve for velocity and plug it into the equation to find acceleration