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The following formulas will be helpful when doing equations. They can also be found at
Physics Formulas and Symbols.

  1. Kinematic Equations

  2. Free Fall from Rest

  3. Dynamics

  4. Atwood Machine

  5. Force and Acceleration

  6. Projectile Motion

  7. Projectile Launched

  8. Momentum

  9. Work and Energy

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 Quantity Symbol Formula
% Error % Error = ( |A-M| ) x 100 /A
% Uncertainty % Uncertainty = (Uncertainty x 100) / Measurement
Distance (Linear displacement) Dd Dd = xf - xo
Elapsed Time Dt Dt = tf - to
Instantaneous Speed V V = Dd / Dt  
(with t approaching zero seconds)
Average Speed Vavg Vavg = (total distance traveled)/(total elapsed time)
Acceleration a a = DV/Dt  =   (Vf - Vo) / (tf - to)
Final Speed Vf Vf = Vo + aDt
 Original Speed Vo Vo = Vf - aDt
Elapsed Time Dt Dt = (Vf -  Vo) / a
Kinematic Equations: ====> (Uniform Acceleration)
Final Velocity Vf Vf = V0 + aDt
Displacement Dd Dd = V0Dt + 0.5(at2)
Final Velocity Vf Vf2  =   V02 +  2aDd
Displacement Dd Dd = 0.5(Vf + V0)Dt
Elapsed Time Dt Dt = (Vf -V0) / a
Free Fall from Rest Vo = 0.0 m/s g =  -9.8 m/s2
Final Velocity Vf Vf =  gDt
 Displacement   Dd Dd = 0.5(gt2)
Final Velocity Vf Vf2  =  2gDd
Displacement Dd Dd = 0.5(Vf )Dt
Elapsed Time Dt Dt = (Vf) / g
Elapsed Time Dt Dt = Sq. root of (2d/g)
  
Dynamics  Equations
Force (Newton's 2nd Law) F = Force F = ma
 Friction Ff Ff = mFn
Newton's Third Law . FAB = -FBA
Weight Fg = F Fg = Fw = mg
 Normal Force Fn Fn = FwCos q  = 
Coefficient of Friction m m= Ff / Fn
Atwood Machine
Net Force Fnet Fnet  =  (M1- M2)g  =  DMg
Acceleration a a = (Fnet ) / (M1+ M2)
Net Force Fnet Fnet = (M1+ M2)a
Mass 1 M1 .
Mass 2 M2 .
Total Mass Mtot Mtot  = M1+ M2
Mass Difference DM DM = M1- M2

Force and
on an

Acceleration
 incline

  
Angle of Incline q q  =  Sin-1(Opp/adj)
Acceleration (net) a a = gsin q
Accelerating Force Fa Fa  =  Fw (Sin q)
Normal Force FN FN = Fw (Cos q)
Vertical Acceleration ay ay = gsinqsinq
Horizontal Acceleration ax ax = gsinqcosq
Projectile Motion
(No Air Resistance!) x = horizontal,
 y = vertical
(Acceleration is in the vertical direction only!)
ax = 0.0 m/s2,  ay = 9.8 m/s2 Down vectors are negative in Value! Subscript "o" means time is 0.0 seconds
    Up vectors are positive in value! Formulas require ay to be positive 9.8 m/s2.   (The negative value has already been entered into the formulas for acceleration!)
Horizontal Motion
xf = xo + Vxot Vxf = Vxo ax = 0.0 m/s2
Vertical Motion      
yf = yo + Vyot - 0.5gt2 Vyf = Vyo - gt V2yf  =  V2yo - 2gDy
         
Projectile Terms and Units:      
xf Final Horizontal Position (meters) Dx = xf - xo =   Vxot
xo Initial Horizontal Position (meters) xo = xf - Vxot
Vxo Initial Horizontal Velocity (m/s) Vxo = (xf - xo) / t  = Vxf
Vxf Final Horizontal Velocity (m/s) Vx= Vxo  =  (xf - xo) / t
ax   Horizontal Acceleration (m/s2) ax = 0.0 m/s2
yf Final Vertical Position 
(m)
Dy = yf - yo  Vyot - 0.5ayt2
 yo Initial Vertical Position 
(m)
yyf - Vyot + 0.5ayt2
Vyo Initial Vertical Velocity (m/s) Vyo = Vyf + ayt
Vyf  Final Vertical Velocity (m/s)  Vyf = Vyo - ayt
Dy Change in Vertical Position (m) Dy = (y - yo)
ay Earth's Gravitational Acceleration (m/s2)  ay = g = -9.8 m/s2
t Time of "flight" (s) t = (Vy- Vyo) / ay
Projectile Launched

 at angle q

 from the horizontal

q Angle of Launch from the horizontal (degrees) q =  tan -1 (Vyo / Vxo)
Vo Resultant Launch Velocity V2o  V2yoV2xo
Vxo Horizontal Launch Velocity (Component) Vxo  = Vo . Cos q
Vyo Vertical Launch
Velocity (Component)
Vyo  = Vo . Sin q
R  (if,  yf = yo) Maximum Horizontal Distance traveled
(or Range)  in meters
R = (V2o Sin 2q) / g

Momentum

(Linear)  Units:            P = kg.m/s     J = N.s
P Momentum P = mV
J Impulse J = F.t
DP Change in Momentum D(mV)  =  m(Vf - Vo)
J = DP Impulse = Change in Momentum F.t  = D(mV)
Ptot = SmnVn Total Initial Momentum m1V1 + m2V2 + m3V3 + .....
P'tot =SmnV'n Total Final Momentum m1V'1 + m2V'2 + m3V'3 + .....
Ptot =P'tot Conservation of Momentum m1V1 + m2V2 + m3V3 + ..... = m1V'1 + m2V'2 + m3V'3 + .....

Explosions and Collisions:

Type:

Momentum Formulas

   Elastic Collision m1V1 + m2V2 = m1V'1 + m2V'2
   Inelastic Collision m1V1 + m2V2 = (m1 + m2)V'f
   Explosion 0 = m1V'1 + m2V'2 + m3V'3 + .....

Work and Energy

(Linear Mechanical System)
Work W W = F.d Cos q
Gravitational Potential Energy Ep Ep = Fw(h) = mgh
Kinetic Energy Ek Ek = (0.5)mv2
Work W W = DEk + DEp
Work W W = DEk + DEp = (0.5mv2 + mgh)f - (0.5mv2 + mgh)
Total Energy (system) SE SE  =  Ek + Ep + heat
Conservation of Energy Initial Total Energy = (SE)i (SE)i = (SE)f
Conservation of Energy Final Total Energy = (SE)f

 or        (Ek + Ep + heat)i  = (Ek + Ep + heat)f

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Last Updated Tuesday, January 3, 2006