Momentum, Impulse, and Collision

Question 1

Characteristic of motion that describes how difficult it would be to stop the moving object; vector quantity

same direction as the velocity

Answer 1

Momentum

Question 2

SI unit for momentum

Answer 2

kg⋅m/s (equivalent to N⋅s)

Question 3

momentum formula

Answer 3

p = mv

Question 4

T or F. Greater momentum → easy to change its state of motion

Answer 4

F. Greater momentum → hard to change its state of motion

Question 5

T or F. Lesser momentum → hard to change its state of motion

Answer 5

F. Lesser momentum → easy to change its state of motion

Question 6

How to change an object’s momentum?

Answer 6

• apply a force
• apply the force at a longer period of time

Question 7

Change in momentum of a particle during a time interval equals the impulse of the net force that acts on the particle during that interval; vector quantity

Answer 7

Impulse

Question 8

Is the direction of impulse the same or different as the net force ΣF?

Answer 8

The direction of impulse is the same as the net force ΣF.

Question 9

SI unit for impulse

Answer 9

N ⋅ s (equivalent to kg ⋅ m/s)

Question 10

Impulse-Momentum Theorem formula/equation

Answer 10

J = ∆p = ΣF(t_2 - t_1)

Question 11

What do airbags and seatbelts in cars do?

Answer 11

increase the time of collision

Question 12

theorem which states that changes in momentum are due to impulse; changes in momentum are due to time over which the force acts

Answer 12

Impulse-Momentum Theorem

J = ∆p = ΣF(t_2 - t_1)

Question 13

theorem which states that kinetic energy changes when work is done; total work depends on distance over which force acts

Answer 13

Work-KE Theorem

W = KE_2 - KE_1 = F(d_2 - d_1)

Question 14

T or F. Conservation of Momentum is important in situations when 2 or more bodies interact.

Answer 14

T

Question 15

Forces that the particles of the system exert on each other

Answer 15

internal forces

Question 16

forces exerted on any part of the system by some object outside it

Answer 16

external forces

Question 17

How can you say if a system is an isolated system?

Answer 17

if there are no external forces and F_int «&laquo_space;F_ext

Question 18

How does the total momentum of the system become constant?

Answer 18

if the vector sum of the external forces on a system is zero

Question 19

total momentum of a system

Answer 19

p = p_A + p_B

Question 20

Impulsive forces in a collision leave the total momentum of the system ____________.

Answer 20

unchanged

Question 21

conservation of momentum formula

Answer 21

mAvA1 + mBvB1 = mAVA2 + mBvB2

A’s, B’s, and the numbers are all subscripts

Question 22

An isolated event where bodies exert a relatively great amount of force to each other over a short period of time

external forces are not considered

Answer 22

Collision

Question 23

Define elastic collision

Answer 23

The momenta and KEs of the bodies may change but the total momentum and total KEs are constant; typically have two unknowns

velocity is not changing; e.g. billiards, collision of particles, etc.

Pi = Pf ; KEi = KEf

Question 24

T or F. The relative velocity of the two bodies has the same magnitude before and after the collision.

Answer 24

T

Question 25

Final velocities in elastic collision, when one body is initially at rest

Answer 25

vA2 = (mA - mB / mA + mB) vA1
vB2 = (2mA / mA + mB) vA1

A’s, B’s, and numbers are all subscripts

Question 26

define inelastic collision

Answer 26

only the total momentum is conserved; total KEs are not conserved (some KE are lost)

ΣKE ≠ constant ; Σp_i = Σp_f

Question 27

Formula for KEi (initial energy)

Answer 27

KEi = KEf + lost energy

Initial energy was transformed to other forms (sound, thermal, etc.)

Question 28

define perfectly inelastic collision

Answer 28

The collision is perfectly inelastic if the bodies stuck together after colliding.

Bodies have same final velocity.

p_1 = p_2

Question 29

Define Center of Mass (CM)

Answer 29

mass-weighted average position of the particles; need not be within the object; behavior of motion of objects is similar to the motion of a particle

Unit: m (meters)