Download EUQATIONS OF MOTION (notes 1-2c)

EUQATIONS OF MOTION
(notes 1-2c)
PHYSICS
BARKER
Essential questions:
1. What are the equations of motion?
2. How do we use the equations of motion?
A. Equations of Motion
1.
Xf
Xi
Vxi
Ax
Vxf
t
D
Xf = Xi + Vxi t + ½ Ax t2
Vxf = Vxi + Ax t
Vxf2 = Vxi2 + 2 Ax D
is final horizontal position
is initial horizontal position
is initial velocity, in the x direction
is acceleration, in the x direction)
is final velocity, in the x direction
is time.
is the displacement, in the x direction, (Xf - Xi)
2. Assumptions:
a. acceleration is
constant.
b. The equations do not
work if the acceleration
is not constant.
3. All the other equations
that describe motion can
be derived from the first
two equations but the
third equation often
reduces the algebra
Will not work for this motion.
required.
B. ACCELERATION DUE TO GRAVITY, g
g, is the symbol used to represent the
acceleration due to gravity on the surface of
the Earth and sometimes used when there is a
constant acceleration, like on the moon’s
surface or any other planet.
1. g = 9.80 m s-2 on the Earth’s surface.
2. gm =1.6 m s-2 on the Moon’s surface.
C. Equations of Motion Using g
1. Vf = Viy – g t
a. The negative sign if up is positive.
2. Yf = Yi + Vyi t – ½ g t2
3. There are slight variations in g due to altitude,
elevation, density of the Earth’s crust, and
proximity to the Equator.