momentum, collisions, explosions Flashcards
what is momentum
momentum is defined as p=mv
What is momentum measured in
Kgm/s or Ns (Newton seconds)
What is impulse
What is the equation
Change in momentum
Pafter - Pbefore
How do you measure impulse on a force vs time graph
Take the integral of the graph
F*T
What does it mean when momentum is conserved? How does it relate to impulse?
When momentum is conserved the change in momentum is 0. So the impulse is 0.
Pafter= Pbefore
Define an inelastic collision, a perfectly inelastic collision, and an elastic collision
Inelastic collision: Momentum is conserved in a closed system. The two objects have different after velocities
Perfectly Inelastic: Momentum is conserved in a closed system. The two object stick together and travel at the same after velocity
Elastic collision: Momentum and kinetic energy is conserved in a closed system
How would you measure if momentum is conserved before and after the collision in 2d collisions? Where all the velocities happen at angles?
You set the before y components of velocity (multiplied by the masses) equal to the after y components of velocity.
You do the same for the x direction
How would you measure if kinetic energy was conserved after a collision
Measure the kinetic energy of the system before the collision and the kinetic energy of the collision after using 0.5mv²
What are the rules for an elastic collision when the two objects of the system have equal masses and mass 1 moves at mass 2 at V1 with mass 2 at rest.
One rule is for head on collsions, one is for 2d collisions.
In a linear collision head on, if mass 1 moved at V1 at mass 2 then mass 1 will be at rest after and mass 2 will move at V1
In a 2d collsion that is not head on, the angles between the after velocities will add up an be equal to 90°
When is momentum conserved, give an example
When the net outside force is zero.
If friction is present momentum is not conserved
What is an explosion
A force that pushes apart two objects that start at rest, or something is being broken into two parts
How does momentum relate to explosions
In an explosion momentum is conserved.
If 2 skaters are standing around, they start from rest, then one skater pushes the other skater, what is true about the after momenta of both skaters?
The momentum of both skaters are equal in magnitude but opposite in direction.
That way when we add them together the momentum of the system is 0, just like the momentum before the explosion
How to calculate the center of mass of a system of objects?
Sum of (m*x) / Sum of masses for the x coordinate
Sum of (m*y) / Sum of masses for the y coordinate
If momentum is conserved, what is true about the center of mass of a collision or explosion
The motion of the center of mass stays the same
