Chapter 6 - Momentum and Collision Flashcards
A common situation dealt with in mechanics is collisions between two or more objects. The actual interactions between the colliding objects can become more complex. To help make sense of collisions you need to utilize the concepts of ________ and ________.
Momentum & impulse
Everything else being equal, it is more difficult to stop an object the more _______ and/or _______ it is.
Massive & faster
The formula for momentum is:
p = mv (kg m/s)
Is momentum a vector or a scalar?
Vector (a product of mass, a scalar, and velocity, a vector)
Since mass is always a positive number, the object’s momentum is always in the same ________ as the object’s ________.
Direction & velocity
A constant net external force acting on an object would change the momentum of the object in a certain amount of time. This is which of Newton’s laws?
Newton’s Second Law (F = change in momentum / change in time)
The product of (F)(change in time) is defined as “_______”
Impulse (I)
With all other things being equal, the larger the applied force, the _______ the impulse and the larger the _______ time of the application of the force, the larger the impulse.
Larger & larger
The units for I are:
kg m/s
Two masses m1 and m2, with m1 < m2, have equal kinetic energy. How do the magnitudes of their momenta compare?
p1 < p2
If the force varies, a modified version of the impulse-momentum theorem must be used - instead of just using force, we need to use an equivalent _______ force that provides the same overall impulse.
Average
The modified impulse-momentum theorem is:
Change in momentum = (average force)(change in time)
The magnitude of the impulse delivered by a force during the time the interval, change in time, is equal to the _______ the force vs. time graph.
Area under
Consider two billiard balls that are coming at each other head on. Let’s assume the effect of friction and air resistance is negligible during the short time of the collision. The weights of the billiard balls are balanced by the normal forces from the table, so there is no ______ on the system consisting of the two billiard balls.
Net force
The total system momentum before the collision is _______ the total system momentum after the collision, as long as there is no net external force on the system.
Same as (m1v1f + m2v2f = m1v1i + m2v2i)
A system that does not have a net external force can be considered an ________.
Isolated system
A collision when kinetic energy is ________ is considered to be inelastic.
Not conserved
Some of the energy in an inelastic collision goes into ______ or ______ the colliding objects.
Sound & deformation
Wnc is not equal to zero, so the mechanical energy is _______.
Not conserved
A perfectly inelastic collision is when:
An inelastic collision where the objects stick together, instead of bouncing off each other
In a perfectly inelastic collision the two objects have _____ final velocity.
The same
Conservation of momentum tells us:
Vf = (m1v1i + m2v2i) / (m1 + m2)
An elastic collision is:
A collision when kinetic energy is conserved
Wnc = 0, so mechanical energy is ______.
Conserved
Atomic and subatomic particles can represent what type of collision?
Perfectly elastic
Conservation of momentum and conservation of energy can tell us:
m1v1i + m2v2i = m1v1f + m2v2f
A car and a large truck traveling at the same speed collide head-on and stick together. Which vehicle undergoes the larger change in the magnitude of its momentum?
The car
An object of mass m moves to the right with a speed v. It collides head-on with an object of mass 3m moving with speed v/3 in the opposite direction. If the two objects stick together, what is the speed of the combined object, of mass 4m, after the collision?
0
Consider two billiard balls approaching each other at different angles relative to the side of the table. Assuming that they do not rotate when they collide, in this case, there are no unbalanced so momentum is _______.
Conserved
Let’s now consider a simpler case where m2 is at rest before the collision and m1 is traveling only along the x axis. This will eliminate some variables, since the initial momentum of m2 is _______ and the _______ component of tour initial momentum for m1 is _______.
Zero, y, & zero
We call the angle of the velocity if m1 with respect to the side of the table after the collision _______ and the angle of the velocity if m2 with respect to the side of the table after the collision _______.
Theta & phi
If a collision is not conserved them the energy is ________.
Not conserved
