Study Guide -- Momentum, Center of Mass (Mr. Rogers AP Physics C )

 Unit Plan Practice Test Study Guide
 Mathematical models
Momentum Impulse
P = mv Imp = DP
Imp = Ft              for constant force

Imp = ∫ F(t) dt
Note: the area under the F vs. time curve equals the change in an object's momentum.

Newton's 2nd Law

Center of Mass

S F = dP / dt
 xcm = (S mixi ) / (S mi ) xcm =1/m  ∫  x dm ycm = (S miyi ) / (S mi ) ycm = 1/m  ∫ y dm

Rockets

Thrust = vm dm/dt
 Key Principles
 Elastic Collision: momentum is conserved kinetic energy is conserved. The particles do not stick together Momentum is a vector: All the rules for vectors apply. For example, when add 2 momentum vectors in different dimensions, you cannot simply sum their magnitudes. You must use vector addition: P = (Px2 + Py2) 0.5 Inelastic Collision: momentum is conserved kinetic energy is not conserved. The particles stick together Explosion of moving objects:If a moving object explodes, the center of mass will continue along the same path as it would have even without the explosion. Rockets:Rockets behave similar to exploding devices. In outer space the rocket's center of mass (including its fuel) will remain in the same location. Rocket thrusters must expel mass to move forward. Impulse and Newton's 3rd Law: When two objects collide the impulse on one is equal in magnitude but opposite in direction to the impulse on the other. Impulse is a vector and Newton's 3rd law applies to it just like it applies to forces.
 Problem Solving Tips: Momentum
 Multi-dimensional momentum problems: Think components! Center of Mass (CM): When calculating the CM, the location of the origin is arbitrary. Always place it in a convenient place that simplifies the problem. Note that the center of mass is like a balance point. If you imagine placing a fulcrum under the CM, the object should look like it is balanced on it.
 Example Problems
 Ballistic Pendulum: The ballistic pendulum uses a combination of conservation of energy and conservation of momentum to find the velocity of a projectile.

 Vocabulary
 Momentum Elastic collision Center of Mass Impulse Inelastic collision
Mr

SAM Team--Southside High School's STEM and Computer Science extra-curricular club (Mr. Rogers Sponsor)

Mr. Rogers Teacher's Blog

Mr. Rogers T-shirts

Mr. Rogers Information for Teachers

Mr. Rogers Science Fair Information

Check out other web sites created by Mr. R:

Check out Articles by Mr. Rogers:

Insultingly Stupid Movie Physics is one of the most humorous, entertaining, and readable physics books available, yet is filled with all kinds of useful content and clear explanations for high school, 1st semester college physics students, and film buffs.

It explains all 3 of Newton's laws, the 1st and 2nd laws of thermodynamics, momentum, energy, gravity, circular motion and a host of other topics all through the lens of Hollywood movies using Star Trek and numerous other films.

If you want to learn how to think physics and have a lot of fun in the process, this is the book for you!

 First the web site, now the book!

Mr. Rogers Home | Common Sylabus | AP Comp Sci I | AP Comp Sci II | AP Physics Mech | AP Physics E&M | AP Statistics | Honors Physics|IB Design Tech | Southside

[ Intuitor Home | Physics | Movie Physics | Chess | Forchess | Hex | Intuitor Store |