Physics Review Flashcards
Formula for Work
W=FcosTHETAd
F=force (kg*m/s^2)
d=distance (m)
Inertia
The ability of an object to resist a change to its velocity
Formula for Center of Mass
Cmass = (r1m1 + r2m2 + r3m3 . . . )/mtotal
r=radius or (displacement vector between reference point and each mass)
Where is center of gravity located?
Exactly at the center of mass
Center of bouyancy
located exactly at the center of mass of the fluid displaced by the submerged
object (NOT at the center of mass of the submerged object itself).
Newton’s first law
An object that is in motion will stay in motion unless acted on by a force. An object at rest will stay at rest “”. Law of inertia
Constant force
A constant net force will always cause a constant acceleration—and therefore a changing velocity.
**A force is not needed to keep an object moving.
Displacement
The shortest distance between point A and point B.
Velocity and Speed
On the MCAT, you can treat “speed” the same as “velocity” if (and only if) the question makes it clear
that the distance traveled is along a straight line.
Constant velocity or constant speed =
1) No acceleration
2) No net force
3) All forces sum to zero (i.e., up forces = down forces, left forces = right forces, etc.)
4) No change in direction
5) The object is in equilibrium
Velocity Formula
V=Delta X/ Delta T
Velocity changes ____ m/s while airborn
10m/s
Average velocity
Vavg = (V1 + V2)/2.
Distance formula
Rate (average velocity) * Time
m/sec sec
EX: V=3m/s T=3s D=9m
Formula for Range
Vx * T
Vx=velocity in x direction T=time
Thoughts for projectile motion
1) Horizontal velocity never changes (as long as you are ignoring air resistance)
2) Horizontal acceleration always = 0
3) Vertical acceleration always = 10 m/s2 downward
4) Vertical behavior is exactly symmetrical (i.e., if ignoring air resistance, a projectile’s upward
trip is identical to its downward trip)
5) Time in the air depends on the vertical component of velocity only
6) Range depends on both the vertical and horizontal components of velocity
7) Time is always the same for both the x and y components of the motion.
Three formulas to know:
X(distance)= (½)at2, Velocity= √(2gh) or Velocity= √(2ax), tair= 2V/g
factors affect the magnitude of air resistance:
1) Cross-sectional Area: greater cross-sectional area = more air resistance
2) Shape: less aerodynamic = more air resistance
3) Velocity: increased velocity = more air resistance.
At terminal velocity:
mg=Fair
Universal Law of Gravitation:
F=Gm1m2/r^2
G=6.67e10^-11 Nm^2/kg^2 (gravitational constant, does not change)
Simplified: F=mg
Formula for potential energy:
PE=mgh
If dealing with a fluid, replace mass with density
PE = ρgh
Formula for Density;
ρ=mass/volume
ρ=density
Formula for potential energy in space:
PE = -Gm1m2/r
Formula for gravity:
g = Gm/r2
Force on an incline plane:
Parallel: F = mgsinθ
Perpendicular: FN = mgcosθ This is =Fn (normal force)
Velocity at bottom of inclined plane:
V = √(2gh)
Hooke’s Law
F = k∆x
k=spring constant
x=displacement of spring from it’s equilibrium position
– the force (F) needed to extend or compress a spring by some distance X scales linearly with respect to that distance.
Elastic Potential Energy: The potential energy
stored in a compressed spring (or in any other
object that follows Hooke’s Law)
PE = (1/2)k∆x2
Simple Harmonic Motion (SHM)
Anything that oscillates back and forth, and can be represented by a sine
wave graphically, constitutes Simple Harmonic Motion.
Formulas for period in spring and pendulum systems
T = 2pi√(m/k) [mass on a spring]
o T = 2pi√(L/g) [pendulum]
Specific gravity:
A ratio that describes how dense something is compared to water.
SG = Dsubstance/DH2O
- For any object floating in any liquid, the ratio of SGobject to SGliquid will exactly equal the
fraction of the object submerged in the liquid.
Buoyancy force:
Fbuoyant = ρvg
v=volume of the fluid displaced not volume of object
- the buoyant force is always exactly equal to the
weight of the amount of fluid displaced by the object
General Pressure Formula:
P=F/A units: pascals, mmHg, atm
Guage pressure:
Absolute pressure is this plus atmospheric pressure
measured with respect to atmospheric pressure, where atmospheric pressure is
defined as zero gauge pressure. Put another way, gauge pressure is the amount of pressure in
excess of the ambient atmospheric pressure.