stuff i need to review Flashcards
(109 cards)
a 2kg ball falls off the roof of a skyscraper that is 500m tall. ignoring air resistance, to what height will it have fallen after 6 seconds?
after 6 seconds ball will be travelling 60m/s
take average velocity- 30m/s
multiply by time- 30x6 = 180m
500-180m = 320m (will be its height)
terminal velocity is reached when?
when F(air) = F(g) when air resistance = gravity
when to use sin and when to use cos in physics equations?
when multiplying two vectors-
if the answer is a scalar, use COS(theta)
if the answer is a third vector, use SIN(theta)
only when you’re multiplying two vectors to start out with!
in physics, when do use sin vs cos in velocity equations specifically?
cos(theta) for when finding horizontal velocity (including normal force ON an inclined plane!)
sin(theta) for vertical velocity (including DOWN an inclined plane!)
you long toss a ball going 60m/s at an angle of 60* to horizontal. ignoring air resistance, what will be its horizontal velocity striking the ground?
v(x) = 60m/s x cos(60) v(x) = 60 x 0.5 v(x) = 30m/s horizontal velocity
a ball strikes the ground going 100m/s. from what height did it fall?
if going 100m/s, it must have fallen 10s ago
100m/s is final velocity, take average- 50m/s
50m/s x 10s = 500m initial height
you throw a rock horizontally going 40m/s from a 125m cliff. how far from the bottom of the cliff does the rock hit the ground?
find time in air first x = 1/2at^2 125 = 1/2(10)t^2 t = 5s horizontal velocity is constant 5s x 40m/s = 200m
a 4,000kg fresh-water fish floats on water and is 1/4 submerged. What is the volume of the fish?
1/4 submerged means that mass of water that would fill 1/4 volume of fish would be 4,000kg
density of water is 1,000kg/m^3
D=m/v
1,000 = 4,000/v –> v = 4m^3
this volume is only 1/4 of fish, so total volume of fish is 16m^3
what is the specific gravity of a liquid in which a boat with a specific gravity of 2.5 is 1/4 submerged?
if ball is 1/4 submerged, then liquid must be 4x dense as the boat. 2.5 x 4 = specific gravity of 10
specific gravity = density / density(water)
25kg ball is placed in unknown liquid and has apparent weight loss of 25N. If the density of the ball is 11g/cm^3, what is specific gravity of unknown liquid?
apparent weight = actual weight - Fb
(so Fb = apparent weight loss)
Fb = pvg (density and volume of fluid, x gravity)
Fb = weight of fluid displaced = apparent weight loss
actual weight of ball = (25)(10) = 250N
ball’s worth of fluid weighs 25N (Fb), while ball weighs 250N
the fluid is 10x less dense than ball
so 11g/cm^3 / 10 = 1.1g/cm^3 is density of fluid
a ball with density of 8x10^2kg/m^3 floats in a liquid with density of 1x10^3kg/m^3. What fraction is above the surface?
liquid density = 1x10^3, ball density = 8x10^2, or 0.8x10^3
this means ball is 0.8 density of liquid
so 0.8 of ball will be below, therefore 0.2 of ball will be above liquid- this is 2/10 or 1/5 of ball
difference between representative heuristic and availability heuristic
representative heuristic: stereotype
availability heuristic: most recent example that comes to mind
stereotype threat vs self fulfilling prophecy
stereotype threat: institutional
self-fulfilling prophecy: individual encounter of someone else imposing stereotype on you
adiobatic
no heat transfer
which of these is soluble:
BaNO3
BaSO4
AgBr
BaNO3- nitrates are always soluble
sulfates not soluble
silver + Cl-, I-, Br- not soluble
what is the centripetal force of your 3kg arm, moving 5m/s, if your arm is 1m long?
F = mv^2/r F = (3)(5^2)/1 = 75N
Ka x Kb?
alternatively, pKa + pKb?
Ka x Kb = 10^-14
pKa + pKb = 14
when is filtration used? when would you use gravity vs vacuum filtration
separate solid from a liquid
gravity: product of interest is in filtrate
vacuum: solid is desired product
are amino groups electron donating or withdrawing
donating
reactivity of metals with water is due to what property of metals?
low ionization energy
in general, all acids react with metal carbonates to form…
CO2 and related salt (decarboxylation)
what can be done to increase percent yield
removal of product
temperature and catalyst affect rate only
temp can also increase Keq (but this is distinct from percent yield)
what is at play during color changes in flame tests and solution chemistry, respectively
flame test = photon emission
solution chemistry = partially filled d orbitals
beta decay
neutron –> proton (antineutrino emitted)
loss of electron