Unit 2: Momentum & Energy
Lesson 1 Applications of Newtons Second Law
F = ma
Dynamics and kinematics
Find the acceleration.
Use the acceleration to calculate some other property of motion.
G.R.A.S.P
Net Force
Free-body diagram
Lesson 2 Applications of Newtons Third Law
For every action there is an equal and opposite reaction.
Tention
Atwood’s Machine
Two masses connected by a strong light string that are hung over an ideal pulley (light and frictionless).
Notice the direction of acceleration and tension.
Objects connected at an angle
Free-body diagram
Lesson 3 Momentum and Collisions
Momentum
The tendency of objects to keep going in the same direction with the same speed.
A property of moving matter.
p = mv
The law of conservation of momentum
The total momentum of the system cannot change when a system of interacting objects is not influenced by outside forces.
Collisions
Momentum is conserved separately in the x and y directions.
Elastic collision - m1v1+m2v2=m1v3+m2v4
Inelastic collsion - m1v1+m2v2=(m1+m2)v3
Lesson 4 Kinetic and Potential Energy
Work
W = Fd
Notice the angle.
Positive work.
Work done on a system that adds energy to the systems.
Negative work.
Work done on a system in which energy is removed from the system.
Kinetic Energy
W = ∆Ek
Potential Energy
Ep = mgh
W = mg∆h2 – mg∆h1 = ∆Eg
Elastic potential energy
Lesson 5 Energy transformations
Conservative vs. Non-Conservative
Conservative Force
Non-Conservative Force
The work done on an object is independent of the pathway taken by the object.
the work done on an object is dependent on the pathway taken by the object.
Types of Collisions
Elastic Collision: Total kinetic energy is conserved
Inelastic Collision: The total kinetic energy is not conserved. Some of the kinetic energy is lost
Completely inelastic collisions: The two objects stick together after the collision
Law of Conservation of Mechanical Energy
The energy remains the same as before a process is done as with after a process is done.
Potential Energy vs. Kinetic Energy
Total Energy = mgh + 1/2mv2
Total energy = 1/2kx2 + 1/2mv2
Conservation of Energy
Total Energy - Wnc = (KEfin – KEinit) + (PEfin – PEinit)
Non-conservation of Energy
W = Wnc + Wc = KEfin - KEinit
Jerry Zou
Power
P = w/t
P = E/t