4 - momentum, machines, and radioactive decay

Question 1

momentum:

Answer 1

is a measure of a moving object’s tendency to continue along its present path.

** p= mv**

Question 2

2 important laws about momentum:

Answer 2

1) momentum is always conserved (isolated system).
2) momentum is a vector.

Question 3

Elastic collisions:

Answer 3

are collisions where the mechanical energy is conserved.

U initial + K initial = U final + K final

Question 4

Inelastic collisions:

Answer 4

occurs when the colliding objects lose some of their mechanical energy to internal energy.

P initial = P final
P (x) initial = P (x) final
P (y) initial = P (y) final

Question 5

Impulse:

Answer 5

is equal to the change in momentum.

J = (delta)p
J = F avg (delta)t
(delta)mv = F avg (delta)t

Question 6

Machines=

Ideal machines=

Answer 6

are mechanical devices that reduce force when doing work.

Ideal machines reduce force but don’t change work.

Question 7

Radioactive decay=

Half-life=

Answer 7

concerns atoms that spontaneously break apart

is the length of time necessary for one half of a given amount of substance to decay.

Question 8

Alpha decay=

beta decay=

poitron emission=

electron capture=

gamma ray=

Answer 8

is probably the easiest to remember. The alpha particle is a helium nucleus (2 protons and 2 neutrons)

is the expulsion of an electron.

the emission of a positron when a proton becomes a neutron

is the capture of an electron along with the merging of that electron with a proton to create a neutron.

is a high frequency photon. Example is when an electron and positron collide.

E = mc^2

Question 9

fusion=

fission=

Answer 9

is the combining of two nuclei to form a single heavier nucleus

the splitting of a single nucleus to form two lighter nuclei