Mcat Physics Lecture 4

Front 1

____ is the tendency for an object to stay in its present state of motion

Back 1

Inertia

Front 2

____ is the tendency for an object to continue moving in its present direction

Back 2

Momentum

Front 3

____ is dependent on a reference frame while ____ is independent of a reference frame.

Back 3

Momentum
inertia

Front 4

Momentum is mass times velocity, it is a ____ quantity, kg m / sec, ____

Back 4

vector
P = mv

Front 5

Total momentum is always conserved in an ____ system

Back 5

isolated

Front 6

Two types of collisions -

Back 6

Elastic
Inelastic

Front 7

____ collisions conserve mechanical energy, (can often conserve kinetic energy but not always)

Back 7

Elastic

Front 8

____ - some mechanical energy is converted to internal energy, so must have at least one nonconservative force acting.

Back 8

Inelastic

Front 9

Another ____ collision is if one of the objects has an increase in temperature due to the collision.

Back 9

Inelastic

Front 10

If there is a permanent deformation of one of the objects, then the collision is ____ (unless the deformed body retained all of the energy as elastic energy)

Back 10

Inelastic

Front 11

____ - when things begin together and push or explode apart.

Back 11

Reverse collisions

Front 12

Always solve reverse collisions with conservation of momentum, ____

Back 12

initial momentum equals final momentum.

Front 13

Ex. An astronaut in space pushing away from his spaceship or man on cardboard on frozen lake throwing rocks.

Back 13

Reverse collisions

Front 14

In a collision problem you will draw two diagrams, one right before the collision and one right after the collision.
If the collision is elastic it is easiest to set the initial mechanical energy to the final mechanical energy.
If the collision is inelastic, you will have to use momentum. (remember momentum is a vector)

Back 14

Initial vertical momentum equals final vertical momentum and
Intital horizontal momentum equals final horizontal momentum.

Front 15

____ is change in momentum

Back 15

Impulse

Front 16

Impulse equals the average force times the time, ____

Back 16

Δmv = fΔt

Front 17

____ is with force versus time graph, the area under the curve is impulse

Back 17

Impulse

Front 18

Or with many bullets hitting a block
The average force of each bullet equals the change in momentum of the block divided by the time from the first collision to the last divided by the number of bullets.

Back 18

Impulse

Front 19

____ cant reduce the work necessary to accomplish a job.

Back 19

Machines

Front 20

Any machine operating under ____ will not change work at all.

Back 20

ideal conditions

Front 21

A ____ machine will increase work.

Back 21

non-ideal

Front 22

Machines reduce ____ not ____.

Back 22

force
work

Front 23

____ = force times displacement, so displacement must be increased to reduce force.
This is the displacement through which the reduced force acts.

Back 23

Work

Front 24

Ramp is a machine -
Want to lift a 5kg box 2m up how much work?
____
Now have a 4m ramp, how much force is required? ____

Back 24

50N times 2m = 100J minimum work required.
25N

Front 25

____ - mass and lever on the same side of the fulcrum, but in opposite directions.

Back 25

Wheelbarrow

Front 26

Lever -
Force times ____ equals torque
Force times ____ clockwise equals force times ____ counterclockwise
The force and ____ are inversely proportional.

Back 26

lever arm
lever arm
lever arm
lever arm

Front 27

Pulley -
Work done on mass is ____, just as like any other mass.

Back 27

mgh

Front 28

In an ____, one rope running through all the pulleys, with the same tension.

Back 28

ideal machine

Front 29

Work done w/ any ____ is the same as moving the mass without the ____.

Back 29

machine
machine

Front 30

Radioactive decay-
Length of time for half of element x to decay to element y is the half-life of element x
Half life = ____
____ is the rate constant of the decay reaction

Back 30

.693/k
k

Front 31

Easiest way for mcat is counting on your fingers.
200g of substance x, halflife is 2 years after 6 years how much is left?
After 10 minutes 2 grams, started with 70 grams how long is the halflife?

Back 31

25g
A little less than 2 minutes

Front 32

4 decay particles:

Back 32

Alpha particles
2 types of beta particles (positrons and electrons)
Gamma particles

Front 33

An ____ is a helium nucleus - two protons and 2 neutrons
If you have a substance undergoing ____ you subtract 4 from its mass number and 2 from its atomic number.

Back 33

alpha particle
alpha particle

Front 34

____ is the creation and expulsion of an electron.
Easiest way to remember ____ is the law of conservation of charge. The net charge of the universe does not change If a negative charge is created a positive charge must be created as well.

Back 34

Beta decay
Beta decay

Front 35

In ____ an electron is emitted and a neutron becomes a proton.
This means that the atomic number increases and mass number stays the same.

Back 35

Beta decay

Front 36

____ is the positively charged counterpart to an electron.

Back 36

Positron

Front 37

In ____ emission a ____ is created and emitted from a nucleus.
So if the net charge of the universe to remain constant, a proton must be destroyed.
____ emission, proton becomes a neutron. The mass number stays the same and the atomic number drops by 1.

Back 37

Positron
Positron
Positron

Front 38

____ - an electron crashes into a proton to form a neutron.
The mass number stays the same and atomic number drops by 1.

Back 38

Electron capture

Front 39

____ - pure energy so it has no mass. So a ____ has no mass number or atomic number.

Back 39

Gamma particle
Gamma particle

Front 40

____ often accompany radioactive decay reactions.

Back 40

Gamma emissions

Front 41

____ produces two gamma particles.
____ is a an electron and positron collision, their mass is destroyed producing two gamma particles.

Back 41

Annihilation
Annihilation

Front 42

_____ do not affect equations.

Back 42

Gamma particles

Front 43

____ is used to find out how much energy is produced by annihilation.

Back 43

E= mc^2
C is the speed of light
M is total mass destroyed

Front 44

Speed of light is ____

Back 44

3.8 x 10^8 m/s

Front 45

E= mc^2 can also be used to find the ____ of the nucleus.

Back 45

binding energy

Front 46

The separate parts of the nucleus weigh less than the whole nucleus.
If you plug this mass defect into e=… you get the ____.

Back 46

binding energy

Front 47

____ is the combing of two light nuclei to produce a more stable heavy nucleus.

Back 47

Fusion

Front 48

____ is the splitting of a heavier nucleus to make a lighter more stable nuclei.

Back 48

Fission

Front 49

When an nucleus undergoes ____, the new bonds are more stable to energy is released.

Back 49

Fission

Front 50

Median nucleus is Fe-56, heavier atoms tend to undergo ____ and release energy
Lighter atoms undergo ____ and release energy.

Back 50

Fission
Fusion