physics Flashcards
if a net force is zero, will the velocity change?
it will be constant and there will be no greater force that needs to be applied
what type of force is a gravitational force?
pulling force
if accel is 0 what does that tell u about velocity?
it is either constant or zero
unbalanced force impacts direction of acceler and?
velocity direction
t or f ? unbalanced force will always change dir?
no bc it could be going on same dir as accell
when there’s a force that hits the center of mass, the forrce will cause?
the object to move in the direction of the force
what happens when force is applied on the object away from the center of mass?
object will then rotate around the center of mass bc of the force that was applied at one of the ends and not the center
when it comes to pulleys. each one has the same or different forces?
same forces
when thinking about the formula for work, what happens to cosine when the force and distance is in the same direction?
cosine will become cosine of 0 degrees or 180 which will become one
normal force means what
normal force is perpendicular to floor/surface making cos 90 deg
gravitational force is perpendic or parallel to surface
perpendicular
how do u increase and decrease the normal force of an object
to increase, you push down on the object
to decrease, you lift up the object like using a tension force which will reduce the stress
why are the weight force/ normal force and the centripetal/centrifugal not part of action reaction pairs?
they cannot be bc together they act on the same object. action reaction means one force acts on one pair of the object while the other force will act on the other object
why are the car tires for a car turning static friction and not kinetic?
it is still driving smoothly to make that turn (friction bc not going straight anymore) but not sliding off of the road which will be kinetic
type of angle btwn accel and velocity in ucm?
perpendicular
why is there change in velocity in circular motion?
constantly changing in direction around the circle
why do u set centripetal force equal to the other forces?
its not a physical force independently but the result of the other forces so it is equal to net force
define closed sys
only exchange energy like earth still getting energy from sun
isolated sys
doesn’t exchange matter or energ
open sys
free to interact with environment
heat vs temp
temp measures thermal energy
heat transfers thermal energy btwn sys and environ
center of mass
the balance point of an object (usually in the moddle)
ignores the rotation of an object
torque and why does it occur
effect of a force (not a force itself) and causes rotation and can measure how fast it rotates
cannot occur when static or without any acceleration
pivot
point that the object will start rotating around
when is torque maximized ?
when force is perpendic to radius bc sin will be 90 deg
T = F * r * sin(theta)
angular acceleration means?
object is not rotating
difference between l and radius of the torque
L is the distance btwn where u apply the force and the axis of rotation
r is the distance from the axis to the line of arm which is parallel to the force???
why is gravity a conservative force?
it is path indep
why is the work for the normal force and the grav force zero?
bc they are perpendic to the surface and cosine of 90 deg is 0
If work is present, what happens to ME
me is not conserved so that means non conserve forces like friction and drag are present
work
energy generated/ transferred by a force
energy
ability to do work
when it comes to an elevator, lmk the tension when its moving up down or not moving
up = tension > force
dwn = tension < force
not moving = tension = force
when it comes to work when will it be zero
when the cos is perpendic (equals 0) so when force and distance make a perpendic
cos goes in same dir of displacement
when finding work with diff cos ang;es and forces
normal force and gravitational force has works of zero becausev cos 90
friction work is neg 1 bc opp dir of cos that aligns with distance being moved
not in all cases bc can change vice versa with elevators
forcs vs displacement graph has slope representing
k the spring constant
work formula for spring
1/2 k (x^2)
conservative force
path independent
ex: gravitational, energy , spring
what does power measure and what is its formula?
it measures the rate of the work that is being done
power= work / time WATTS = J/s
when does the instantaneous power = avg power
when given powers were the same during each time period
instantaneous power
fdcoso / t
force (cos angle btwn force and speed) ( speed )
if force is in same dir as the speed, cos will be 1
mechan advantage formula
work in = work out
fd = fd
when lose polarity or pos charges move to neg what happens to the voltage
dec
avg sodium and potassium level in extracellular fluid
150 mg/L sodium
5mg/L potassium
2 types of fluid
gas and liquid
pressure formula
force/ area = n/m^2
volume of sphere formula
V=4/3 (πr^3)
area of circle
pi r^2
volume of fluid
area x distance
pascal principle formula
for fluids with external pressure meaning a pressure of external force was applied :
pressure in = pressure out
work in = work out
unit for pressure is pascals
ex: applies to finding pressure volume etc
F1/ A1= F2 / A2
the deeper u dive in water, what happens to pressure
it incr
internal pressure of fluid
pressure = density of water x height x gravity
density of h20
1000 kg / m^3
spec gravity
density of substance / density of water
no units bc ratio of density
u use spec grav bc it tells u how much of object will be submerged while floating in the water
if value is > 1 then obj will sink so 100% of it will submerge
OR to float, its density has to be less than that of air or water density
how to get density from specific gravity
multiple specif density of substance by the density of water which is 1000 kg / m^3
1 atm = how many pascals and kpascals
1 atm = 101 kPa
1 atm = 100,000 Pa
buoyant force
F= mg F= density x volume that is submerged (water displaced) x gravity
F= wt of substance out of water - wt inside of water
has an upward force in water to counteract the downward wt of the substance
laminar flow vs turbulent
During turbulent flow ,first of all, the velocity of fluid flow will be higher. Turbulence is induced by roughness of the pipe surface. With the higher velocity at outlet than at inlet you will have different volume of liquid in and out. That’s why Sal mentions that for equal volumes to come in and out the flow should be laminar.
laminar is even so volume in = volume out
A1V1 = A2V2
viscous fluid
turbulent flow with friction or resistance
flux meaning and formula
how much of volume crosses in an amount of time
input volume/ second
m^3 / sec
when dealing with burnoili equation,
what will happen to potential energy if the heights are even?
what would happen to pressure when there is no potential energy, higher velocity?
with equal height, potential energy cancels out
the pressure will decrease
compare viscosity of liquid vs gas
viscosity is resistance to flow
so gas will have less viscosity than liquid because it has less order and more random movement
unit: pa x second
= pouise which = 1/10 of pa x sec
no viscosity means no force needed to continue flow but usually not the case bc viscos is seen all the time and will cause pressure diff to help continue flow
3 things to keep in mind with Pouseille’s law volume blood flow rate (Q)
pir^4(Pressure1 - pressure 2) /8nL = Q
increasing the blood vessel’s radius by let’s say a factor of 2 would increase it’s blood flow (Q) by a factor of 16
increases the length decreases the blood flow rate
increasing the pressure change increases the bllod flow rate bc keep in mind things with high pressure in fluids will have low speed bc harder to move through