Unit 5 - Momentum (12-18%)

Question 1

momentum definition

Answer 1

a physics term that refers to the quantity of motion that an object possesses (aka “mass in motion”)

Note: considered a vector quantity because it has direction, which depends on the direction of the velocity

Question 2

two things that increase an object’s momentum:

Answer 2

more mass and more speed (velocity)

Question 3

momentum formula and its unit

Answer 3

momentum = mass * velocity (p=mv)

kg m/s or N/s

Question 4

impulse definition and equations

Answer 4

the product of the net force acting on an object and the time interval over which that force acts (change in momentum)

(delta p = mass * delta v, delta p = force * delta t, delta p = m vfinal - m vinitial)

Question 5

two types of graphs related to momentum and how to interpret them

Answer 5

force vs. time graph (area is impulse or change in momentum)

velocity vs. time graph (use to find v initial and v final)

Question 6

how can an egg have the same impulse when dropped vs. dropped in water but not always break?

Answer 6

same impulse, but since impulse is force times delta t, there’s less force applied over a greater time

Question 7

changes in momentum with two objects equation

Answer 7

momentum of system = m1v1 + m2v2

Question 8

law of conservation of momentum and equation

Answer 8

momentum before collision equals momentum after as long as no net external force is applied to system

m1v1 initial + m2v2 initial = m1v1 final + m2v2 final

Question 9

closed system

Answer 9

momentum is conserved before/after collision, free of external forces like friction

Question 10

open system

Answer 10

momentum is not conserved before/after collision, external forces are present

Question 11

elastic collisions

Answer 11

objects hit and bounce, kinetic energy is CONSERVED

Question 12

inelastic collisions

Answer 12

hit and bounce, hit and stick, or hit and explode, kinetic energy is NOT CONSERVED

Question 13

rule for changes in momentum of a system:

Answer 13

the momentum of a system can be changed if a net external impulse is applied to that system

Question 14

strategies for problems (just read them)

Answer 14

draw a diagram pre/post collision, start w/law of conservation of momentum, include unknown quantity, remember what direction object is going (+ or -)

Question 15

4 steps for solving for kinetic energy lost in inelastic collision

Answer 15

calculate initial kinetic energy before collision, solve for final velocity w/law of conservation of momentum, calculate total kinetic energy after collision, subtract final KE from initial