Physics Review

Question 1

Significant Digits

Answer 1

• Digits 1 to 9 are always significant digits
• Leading 0’s are not significant, trailing zeros are always significant
• When adding or subtracting numbers, the number of digits behind the decimal in the answer should be equal to the least number of digits behind the decimal in the question
• When multiplying or diving numbers, the number of significant digits in the answer should be equal to the least number of significant digits in the least number

Question 2

Scalar Quantities

Answer 2

Have magnitude only and do not include direction
- Distance, speed, time, work, mass

Question 3

Vector Quantities

Answer 3

Have both magnitude and direction
- Displacement, velocity, acceleration, force

Question 4

Distance

Answer 4

Scalar quantity that describes the length of a path between two points. SI unit is meters (m)

Question 5

Displacement

Answer 5

Vector quantity that describes the straight-line distance from one point to another, as well as direction. SI unit is second (m)

Question 6

Time

Answer 6

Scalar quantity that describes a specific point in time. SI unit is second (s)

Question 7

Speed

Answer 7

Scalar quantity that describes the distance travelled by an object during a given time interval. SI unit is meters per second (m/s)

Question 8

Velocity

Answer 8

Vector quantity that describes the displacement of an object during a given time interval. SI unit is meters per second (m/s)

Question 9

Acceleration

Answer 9

Vector quantity that describes any change in the velocity of an object during a given time interval. Non-uniform motion because velocity is not constant.

• Although acceleration points in the same direction as the CHANGE in velocity, it’s not always in the same DIRECTION as the velocity itself
• Acceleration in the same direction of velocity = Speeds up
• Acceleration in the opposite direction of velocity = Slows down

Question 10

Force

Answer 10

Vector quantity that describes a push or pull that must be exerted on an object in order to make the object move. SI unit is newton (N) or kilogram meter per second squared (kg * m/s^2)

Question 11

Issac Newton

Answer 11

Described the relation between force and motion, in his 3 laws of motion
1) Law of Inertia - Every object in motion will remain in motion and every object at rest will remain at rest unless acted upon by an outside force; friction and gravity
2) F=ma - Force needed to change an objects motion is proportional to its mass and its acceleration
3) Reactions - For every action there is an equal and opposite reaction

Question 12

Force of gravity

Answer 12

The force of gravity acting on an object. SI unit is Newton (N) or kilogram meter per second squared (kg*m/s^2)
- Force of gravity on earth = 9.81 m/s^2

Question 13

Work

Answer 13

Scalar quantity that describes the energy transfered to or from an object when a force is applied to move the object. Work is done when an object moves in the direction of the force that is being applied. SI unit is Joule or kilogram meter squared per second squared (kg * m^2/s^2)

Question 14

Graphical determination of work

Answer 14

Total work done by the force can be determined from the area under the curve of a force vs. distance graph

Question 15

Kinetic energy

Answer 15

The energy of motion

Question 16

Bulk Kinetic Energy

Answer 16

Energy due to the motion of a whole object
- Larger the mass or faster the object, the more bulk kinetic energy it has

Question 17

Electric Energy

Answer 17

Energy carried by moving electric charges
- Eg. Lightning as a result of moving electrical charges

Question 18

Thermal Energy

Answer 18

Energy due to the random motion of the molecules that make up an object

Question 19

Sound Energy

Answer 19

Energy carried from molecule to molecule by longitudinal waves

Question 20

Radiant Energy

Answer 20

Energy that travels as electromagnetic waves
- Eg. Sun is our largest source of radiant energy

Question 21

Potential Energy

Answer 21

The energy that can be stored in an object for a long period of time. This stored energy can be transformed into a form of energy that can do work

Question 22

Gravitational Energy

Answer 22

Energy as a result of an object’s distance above the Earth

Question 23

Elastic Energy

Answer 23

Energy stored in an object when it is forced out of its normal shape

Question 24

Chemical Energy

Answer 24

Energy stored in molecules (bonds between atoms)
- This energy is released when a chemical reaction occurs and bonds are broken

Question 25

Nuclear Energy

Answer 25

Energy stored in the nucleus of an atom
- Released during nuclear fission, when a large nucleus breaks apart
- Released during nuclear fission, when small nuclei join together

Question 26

First Law of Thermodynamics

Answer 26

Energy is conserved in a closed system. This means that energy cannot be created or destroyed, only transformed from one form to another or from one object to another
- The total energy of the universe is constant

Question 27

Free Fall Question

Answer 27

Em = Ep + Ek
- When height is max, Ep = max, Ek = 0, Em = Ep
- When height is 0, Ep = 0, Ek = max, Em = Ek
- There is a middle point where Em = Ep + Ek
Em before = Em after
Ep + Ek = Ep + Ek
mgh + 0 = 0 + mv^2/2
gh = v^2/2
(masses cancel out in freefall questions)

Question 28

Four Elements Theory

Answer 28

• All matter consists of a combination of four elements: earth, air, fire, water
• When objects burn, the fire inside of them is released

Question 29

Phlogiston Theory

Answer 29

• Substances that could burn contained an invisible fluid called phlogiston, that flowed out of an object when it burned
• Problem: Theory implies that the mass should decrease when an object burns, but magnesium gains mass when it burns

Question 30

Caloric Theory

Answer 30

• Caloric is a mass-less fluid found in all substances, that flows from one substance to another to another. The flow is always from warmer to cooler objects
• Problem: When holes are bored into metal to make a cannon, the metals were not hot to start with but became hot afterwards

Question 31

Rumford’s Hypothesis

Answer 31

• When holes are bored into metal to make a cannon, the mechanical energy is converted into heat, therefore Heat = Energy
• Problem: Caloric theory was so popular that Rumford was ignored

Question 32

Mayer’s Hypothesis

Answer 32

• Recognized that the body uses oxygen to break down food for energy, and that this same process provides heat. Discovered that bodies in colder climates use more oxygen and generate more heat than bodies in warmer climates. Further support to Rumford’s idea that Heat = Energy
• Problem: Mayer was not schooled in math or physics so his ideas were overlooked because his presentation was poor

Question 33

Joule’s Theory

Answer 33

• Proved the relationship between mechanical energy and heat, using the following experiment:
  1) Force of gravity causes the weight to fall
  2) Falling weight pulls on the string, which turns the drum
  3) Turning of the drum stirs the water
  4) The motion of the stirrer transfers energy to the water, which causes the temperature of the water to increase
• Force of gravity indirectly does work on the water
  Ep (weight) → Ek (weight, drum, stirrer) → Thermal Energy (water)

Question 34

Kinetic Molecular Theory

Answer 34

• The molecules of a liquid or gas are in constant random motion. Kinetic energy is the energy of motion. The molecules in a solid vibrate
• As the molecules move in a straight line, they collide with each other and with the walls of the container
• Heat - The transfer of thermal energy from one object to another
• Temperature - The average kinetic energy of the individual atoms or molecules in a substance

Question 35

Steam Engine

Answer 35

• Any machine that generates steam and converts the steam pressure into mechanical motion
  Heat → H20 (l) → H2O (g) → Pressure → Mechanical Motion

Question 36

Second Law of Thermodynamics

Answer 36

No process is 100% efficient. Some energy is always lost as thermal energy.