Unit B: Physics

what is the formula for speed?

v=d/t

formula for distance (honors):

d = vit + 1/2at²

formula for average speed (honors):

vi + vf / 2

formula for final speed (honors):

vf² = vi² + 2ad

motion with a constant speed in a straight line

uniform motion

what are the y and x axises for distance-time graphs?

y = distance

x = time

what does Δ mean?

delta: change in smt

formula for slope:

rise/run

what do we use the slope for in a distance-time graph?

to determine the speed

what does it mean when a slope is zero?

line is horizontal, motion is uniform, nothing changes

how do you find the area of a graph?

a = l x w (y axis x x axis)

if its not a horizontal line use bh/2

what are the two systems to describe a vector for direction??

degrees from the x or y axis (10km, 80° E of the -y axis)

degrees using compass directions (10km, 80° E of S)

rate of motion of an object

speed

both the rate of motion and the direction of the objects motion, making it a 😝 quantity

velocity, 😝 = vector

magnitude = ?

amount

scalar quantities only have:

magnitude

t or f: distance is a scalar quantity (magnitude only)

true

t or f: displacement is a scalar quantity (magnitude only)

false, it is a vector quantity meaning it has magnitude and direction

formula for velocity:

v = d/t (v and d have an arrow over them)

v w/ arrow: velocity

d w/ arrow: displacement

t: time

what is very important when writing velocity or displacement?

to have a direction

ex: displacement is 465 km [S]

ex; velocity is 558 km/h [S]

sum or two or more vectors

resultant

how to i find the resultant of vector quantities that are in the same direction?

you add them

ex: A person runs 25m south and then another 15m south.

25m + 15m = 40m

how to i find the resultant of vector quantities that are different directions?

you subtract them

ex: A plane flies 200km north and then turns around and comes back 150 km.

200km [N] - 150km [S] = 50km [N]

change of velocity over time

acceleration

look at page 13 in the notes to see the types of graphs

formula for acceleration:

a = v_f - v_i / t

a: acceleration in m/s²

v_f : final speed (velocity) in m/s

v_i : initial speed (velocity) in m/s

example of a problem on pages 14-15 in the notes

what happens when force is in the same direction as motion?

object gains energy and speeds up

what happens when force is opposite to motion?

object loses energy and slows down

what creates heat when force is applied?

friction

3 conditions for work that must be there:

1. there must be movement

2. there must be force

3. the force and movement must be in the same direction

energy put into something

work input

useful energy the object acc gets

work output

if there is no friction, work input then =

work output

what does acceleration due to gravity equal?

9.81m/s²

if an object is falling (acceleration due to gravity):

if an object is going up:

9.81 m/s²

-9.81m/s²

a push or pull

force

is the resultant force when vectors that are equal in magnitude but opposite in direction are added together, therefore they cancel each other out

balanced force

is the resultant force when vectors that are not equal in magnitude or not opposite in direction are added together, therefore they do not cancel each other out

unbalanced force

formula for force:

F = ma

m = mass in kg

a = acceleration in m/s²

F = force in Newtons (N)

is the force due to gravity

weight

formula for work:

W = Fd

W = mad

W = wrok in Joules (J)

F = force in Newtons (N)

d = distance in m

m = mass in kg

a = acceleration in m/s²

ability to do work

energy

potential energy stored in chemical bonds of compounds

chemical energy

work done by moving electrons

electrical energy

magnetism on page 19 notes

energy stored in the nucleus of an atom, energy is released when the nucleus is split or when two nuclei combine

nuclear energy

energy from the sun, created usually through nuclear fusion, reaches the earth as electromagnetic radiation

solar energy

energy of an object because of the movement of atoms (heat)

thermal energy

faster moving particles =

more heat

is energy where there is no motion, there is potential because of its position

potential energy

5 types of potential energy:

1. gravitational energy

2. chemical energy

3. elastic energy

4. nuclear energy

5. electrical energy

energy stored due to the height of an object

gravitational potential energy

formula for gravitational potential energy:

E_p = mgh

E_p = Fh

m = mass in kg

g = acceleration due to gravity = 9.81 m/s²

h = height in m

E_p = gravitational potential energy in J

F = weight in N

energy of motion

kinetic energy

4 types of kinetic energy

1. mechanical E_k

2. thermal E_k

3. sound E_k

4. electrical E_k

formula for kinetic energy:

E_k = ½ mv²

E_k = kinetic energy in J

m = mass in kg

v = speed in m/s

total energy of an object because of movement

mechanical energy

formula for mechanical energy:

E_M = E_K + E_P

E_M = 1/2mv² + mgh

READ PAGES 23-24 FOR THE LAWS OF THERMODYNAMICS AND ENERGY CONVERSIONS

first law of thermodynamics:

energy cannot be created or destroyed, only changes form

total energy input = total energy output

second law of thermodynamics:

energy is ALWAYS lost in heat (friction) because it is in every conversion

set of interconnected parts

system

system that exchanges both matter and energy with its surroundings

open system

system that only exchanges energy with its surroundings

closed system

system that does not exchange matter or energy with its surroundings

isolated system

4 pieces of evidence energy conversions:

1. motion

2. change in energy

3. change in motion

4. change in shape

Read the energy conversion systems from page 25-26

read about efficiency on page 26 of the notes

formula for efficiency:

% efficiency = (useful output/total input) x 100

derived either directly or indirectly from the energy of the sun

solar energy sources

solar, wind, geothermal, tidal, biomass

examples of renewable resources

Force due to gravity

Weight

If a question gives you force due to gravity, what does that represent (what number do you use?)

Acceleration due to gravity

9.81m/s²