Chapter 6 - Momentum and Collision

Question 0

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 ________.

Answer 0

Momentum & impulse

Question 1

Everything else being equal, it is more difficult to stop an object the more _______ and/or _______ it is.

Answer 1

Massive & faster

Question 2

The formula for momentum is:

Answer 2

p = mv (kg m/s)

Question 3

Is momentum a vector or a scalar?

Answer 3

Vector (a product of mass, a scalar, and velocity, a vector)

Question 4

Since mass is always a positive number, the object’s momentum is always in the same ________ as the object’s ________.

Answer 4

Direction & velocity

Question 5

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?

Answer 5

Newton’s Second Law (F = change in momentum / change in time)

Question 6

The product of (F)(change in time) is defined as “_______”

Answer 6

Impulse (I)

Question 7

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.

Answer 7

Larger & larger

Question 8

The units for I are:

Answer 8

kg m/s

Question 9

Two masses m1 and m2, with m1 < m2, have equal kinetic energy. How do the magnitudes of their momenta compare?

Answer 9

p1 < p2

Question 10

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.

Answer 10

Average

Question 11

The modified impulse-momentum theorem is:

Answer 11

Change in momentum = (average force)(change in time)

Question 12

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.

Answer 12

Area under

Question 13

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.

Answer 13

Net force

Question 14

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.

Answer 14

Same as (m1v1f + m2v2f = m1v1i + m2v2i)

Question 15

A system that does not have a net external force can be considered an ________.

Answer 15

Isolated system

Question 16

A collision when kinetic energy is ________ is considered to be inelastic.

Answer 16

Not conserved

Question 17

Some of the energy in an inelastic collision goes into ______ or ______ the colliding objects.

Answer 17

Sound & deformation

Question 18

Wnc is not equal to zero, so the mechanical energy is _______.

Answer 18

Not conserved

Question 19

A perfectly inelastic collision is when:

Answer 19

An inelastic collision where the objects stick together, instead of bouncing off each other

Question 20

In a perfectly inelastic collision the two objects have _____ final velocity.

Answer 20

The same

Question 21

Conservation of momentum tells us:

Answer 21

Vf = (m1v1i + m2v2i) / (m1 + m2)

Question 22

An elastic collision is:

Answer 22

A collision when kinetic energy is conserved

Question 23

Wnc = 0, so mechanical energy is ______.

Answer 23

Conserved

Question 24

Atomic and subatomic particles can represent what type of collision?

Answer 24

Perfectly elastic

Question 25

Conservation of momentum and conservation of energy can tell us:

Answer 25

m1v1i + m2v2i = m1v1f + m2v2f

Question 26

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?

Answer 26

The car

Question 27

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?

Answer 27

0

Question 28

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 _______.

Answer 28

Conserved

Question 29

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 _______.

Answer 29

Zero, y, & zero

Question 30

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 _______.

Answer 30

Theta & phi

Question 31

If a collision is not conserved them the energy is ________.

Answer 31

Not conserved