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