Week 2

Question 1

What is momentum?

Answer 1

Inertia of motion
- the tendency of a moving object to resist change to its motion
Momentum = mass x velocity
Momentum is directly proportional to both mass and velocity
Stationary objects can’t have momentum because their velocity is 0

Question 2

Explain the relationship between momentum & net force

Answer 2

Acceleration is always the result of a net force
- if acceleration occurs, then a change in velocity occurs
- if velocity of an object changes, its momentum must also change as a result
Therefore a net force causes a change in momentum of an object
- the greater the force , the greater the momentum change
🔺M directly proportional to F

Question 3

How is the change in momentum and time related?

Answer 3

The longer the duration of time that a net force is applied, the greater the change in momentum
🔺M is directly proportional to time

Question 4

What is impulse?

Answer 4

Since the change in momentum (🔺M) is proportional to both net force (F) & the time of applying the force, we can state this as a propotionality statement
🔺M is directly proportional to Ft
Ft is called impulse
Impulse = net force x time interval
Impulse is the change in momentum

Question 5

How is impulse and momentum change combined?

Answer 5

Impulse = change in momentum
Ft = 🔺mv
Impulse & change in momentum can hep explain how to control the change in motion & effect of an applied force

Question 6

How can momentum be increased in a tennis swing example?

Answer 6

Maintaining racquet-ball contact for longer by swinging the racquet through guiding the ball until it leaves

Question 7

What is work?

Answer 7

The ability to move an object against a force
Work (W) is the product of the force (F) on an object & the distance (d) through which the object is moved by that force W=Fd
When we ‘do work’ on an object, we change the objects energy situation
Unless the object changes location as a result of an applied force, no work is done

Question 8

When is work done?

Answer 8

Work is done against another force
Work can be done to change the speed of an object (increasing or decreasing)
- Proof of work is that the objects position changed relative to what it would’ve otherwise been

Question 9

How is work measured?

Answer 9

W = F x d
Right side of equation is in N x m which means the left will have the same unit
Joule (J) is the derived (meaning produced from the combination of base units) unit for work
1J = 1N x 1m

Question 10

What is power?

Answer 10

The quantity of work done per unit time
P = W/t
Measuring power: Since power = work in J/time in secs, power could be measured in J/s
The derived unit for power is the Watt (W)
1W = 1J/1sec

Question 11

What is energy?

Answer 11

The ability to do work
When energy is acquired by an object, it can then do work on another object if conditions allow it
Work shifts energy from one system to another
Energy takes many forms
Energy is measured in J

Question 12

What is mechanical energy?

Answer 12

Mechanical = moving
Mechanical energy is the energy due to an objects movement & relative position
Takes 2 forms:
- Potential: Due to relative position
- Kinetic: Due to motion

Question 13

What is potential energy (PE)?

Answer 13

When an object has done work on it to put it in a certain position relative to another location, thee object stores that energy as ‘potential energy’

Question 14

How is energy stored?

Answer 14

By doing work on an object to put it in a location (or position), then restraining the object in that location, the object stores the energy as long as it stays at that location

Question 15

What is kinetic energy?

Answer 15

If an object is moving, it is capable of doing work, so it must have energy
The object received the energy from the thing that caused it to be put in motion. While its in motion, it holds the energy in kinetic form
Some or all off that energy is transferred when the object interacts (e.g collides) with another object
KE is work that the object can do while being brought to rest

Question 16

What factors affect kinetic energy (KE)?

Answer 16

The quantity of KE the object has while moving depends on 2 things:
Mass Velocity
KE = 1/2 mv^2
KE is directly proportional to both, but exponentially to velocity

Question 17

What must happen for an object to get KE?

Answer 17

An object must receive energy from another source in order to move
- work must be done on it
The quantity of work is the amount needed to change the objects state from being at one state of motion to that new velocity
- that requires an external force to be applied
- the more force applied, the more KE imparted
This makes sense since work = force x distance

Question 18

How are KE and work related?

Answer 18

KE = 1/2mv^2
We also know that KE = work done on the object to make it move at that velocity
- Work = force x distance
Combined:
Work = 🔺KE
Force x distance = KE final - KE initial

Question 19

What is the sum of mechanical energy?

Answer 19

As an object changes its relative position its PE is changing in magnitude
As it changes position its also moving, so it also has KE
The sum of PE & KE is the total mechanical energy of the object
During the motion, the levels of PE & KE will both change, but their sum will be constant until the object does work on something else (& therefore transfers so energy)

Question 20

What is the bohr model of an atom?

Answer 20

The simple model is an approximation of a more correct theory (quantum mechanics)
Termed ‘planetary’ or ‘solar system’ model due to resemblance to planets orbiting around the sun

Question 21

What does the structure of an atom include?

Answer 21

Nucleus
-densely packed central area of an atom
- contains 2 types of fundamental particles: proton & neutron

Orbitals (shells)
-region around nucleus where electrons can travel
-each orbital has a specific radius
-‘shell’ term indicates that the orbital is a 3D space where the electron is permitted to exist
- the shell isn’t a real structure though

Question 22

Explain more about orbital

Answer 22

Each orbital is a specific 3D location relative to the nucleus
- that means the electrons allowed in each orbit have specific PE levels due to their relative location
Each orbital has a specific max number of electrons that can occupy it

Question 23

What are the 3 fundamental particles, and their approx mass in amu and atomic number?

Answer 23

Neutron (n) Electrostatic Charge: 0 Approx mass in amu: 1 Atomic mass #: 1
Proton (p^+) Electrostatic Charge: 1+ Approx mass in amu: 1 Atomic mass #:1
Electron (e^-) Electrostatic Charge: 1- Approx mass in amu: 1/1837 Atomic mass #:0

Question 24

Tell me about the number of particles in an atom

Answer 24

In an atom with a balance of charge (pos vs neg), the number of orbital electrons is = to the number of protons in the nucleus
The number of neutrons is close to or the same as the number of protons
- depends on the specific type of atom (specifically, which element)

Question 25

What is an element?

Answer 25

A material comprised entirely of 1 type of atoms (all having the same number of protons)
-can’t be broken down into any simpler substance
The atom is the smallest identifiable unit of an element
Each element has an ‘atomic number’ (Z) that is the sum of the protons
Each element has multiple versions of its nuclear contents (varying number of neutrons & varying quantities of energy within the nucleus BUT same number of protons)
- these versions are called ‘isotopes’ of the element

Question 26

What is a compound?

Answer 26

Consist of atoms of 2 or more different elements bound together
Have chemical properties that are different from each of their constituents
The only way to break up a compound is to use chemical means

Question 27

What is a mixture?

Answer 27

Combination of different elements but without the chemical bonding between the different elements

Question 28

What is a molecule?

Answer 28

A group of 2 or more atoms bound together with shared electrons, & has no net charge (that means a balance of + & - charge)
They may be multiple atoms of a single element or multiple elements
The molecule is the smallest unit of a compound that still has the chemical properties of that compound

Question 29

What is matter? What are the states of matter?

Answer 29

Matter: Anything that occupies space (has volume) & has mass. It’s made up of atoms
4 states of matter: Solid, gas, liquid, plasma
Matter can undergo a ‘physical change’ to change its state from 1 to another
- Normally accomplished by temp change

Question 30

What are the fundamental properties of a solid?

Answer 30

Maintains fixed volume & shape regardless of container
Changes shape only when cut or broken
Component particles (atoms, molecules & ions) are close together & in fixed spatial relationships to one another
Component particles vibrate in place

Question 31

What are the fundamental properties of a liquid?

Answer 31

Is nearly compressible
Maintains a relatively fixed volume regardless of pressure but has a variable shape that adapts to its container
Component particles (atoms, molecules & ions) are close together but move freely relative to one another

Question 32

What are the fundamental properties of gas?

Answer 32

Takes the volume & shape of container
Component particles (atoms, molecules & ions) are relatively far apart & move freely relative to 1 another with virtually no inner-molecular interaction

Question 33

What are the properties of solids (more detailed)?

Answer 33

Solids may be crystalline or amorphous
Crystalline solids:
- most solids have a 3D lattice structure
- this lattice is a repeating pattern of arrangements of specific atoms
- the atoms are held in their relative locations by inter-atomic forces
Amorphous solids have a random arrangement of atoms that have some ability to relocate

Question 34

What is volume?

Answer 34

The measure of the 3D space occupied by an object
SI units are m^3 (cubic meters)
- a common non-SI unit is the litre
The volume of an object is dependent on several factors:
- Quantity of matter (mass), pressure (for gases), temp, state or phase, deformation by forces

Question 35

What is density?

Answer 35

The mass per unit volume of a material
Customary symbol for density is Greek letter ‘rho’: p
- p =m/V, where m=mass v=volume
SI unit of density is kg/m^3
Density depends on:
Contents of the atoms in the material, spacing of the atoms
Density is relatively fixed for solids & liquids but unfixed for gases because they take the volume of their container

Question 36

What is elasticity?

Answer 36

The relative quantity of temporary change to an objects shape that occurs in response to the application of a deforming force to it
- when the force is removed, the objects shape would be restored
‘Inelastic’ material doesn’t resume its original shape when the force is removed

Question 37

What are deforming forces?

Answer 37

Deformingforces can be compressing or stretching in effect
A force that increases the objects dimension is a ‘tension’ force
A force that decreases the objects dimension is a ‘compression’ force
Work is done on an object in causing compression & stretching (since force is applied along a distance)
- the objects energy situation changes as a result

Question 38

Why do deforming forces matter?

Answer 38

It’s a key concept for the production of sound & its movement through mater
The response of specific body structures (e.g bone) to deforming forces has clinical relevance

Question 39

What is centrifugal force?

Answer 39

A force that is center directed, an occupant inside a revolving or rotating system seems to experience an outward force.

Question 40

What is gravitational force?

Answer 40

An interaction between 1 mass & another. The gravity we experience is our interaction with earth. But for centrifugal force in the rotating frame, no such agent exists - there is no interaction counterpart. Centrifugal force feels like gravity, but theres no something pulling. The force
felt is a result of rotation.

Question 41

What is Inertial force (fictitious force)?

Answer 41

An apparent force - & not a real force like gravity, electromagnetic forces, & nuclear forces.

Question 42

What is the relationship between centrifugal acceleration and radial distance?

Answer 42

Centrifugal acceleration is directly proportional to the radial distance from the hub