Unit 3:Kinematics & Free Fall
Sprayberry
Physics
Physics Comp BookUNIT 3: Kinematics & Free-Fall Student will: compare algebraically the relationships between
time, distance, velocity and acceleration; compare and contrast scalar and vector quantities.
Page Contents 17 kinematics, free fall 18 gravity, gravitational acceleration, 19 air resistance 19 kinematics formulas—x and y directions 20 Ex: solving a kinematics problem 20 Lab SUMUP:
* How tall is the stadium?
p. 16
Frayer for kinematics
kinematics
describes the motion of objects without consideration of the causes leading to the motion
kinematics:
All the ways to describe motion in a mathematical way:
motion math
Example Problem:
time =
displacement =
velocity-initial =
velocity-final =
acceleration =
Kinematic Equations
Copy these into your comp book at the bottom of p. 19
2
)(2
22
22
tvvx
attVx
xaVV
atVV
fi
i
if
if
2
)(2
22
22
tvvy
gttVy
ygVV
gtVV
fi
i
if
if
Kinematic Equations - Ex #1
A car traveling with an initial velocity of 6 m/s, accelerates at 2 m/s2, for 6 seconds. What is the car’s final velocity?(1) LIST (3) Equation
(2) LABEL w/units (4) SolveAre we working in the x or y direction?
s
mV
atVV
f
if
18)6*2(6
Kinematic Equations - Ex #2
A car traveling with an initial velocity of 6 m/s, accelerates at 2 m/s2, for 6 meters. What is the car’s final velocity?
(1) LIST (3) Equation
(2) LABEL w/units (4) Solve
s
mV
V
V
xaVV
f
f
f
if
746.760
602436
)6*2*2(6
2
2
22
22
Kinematic Equations - Ex #3
A car traveling with an initial velocity of 6 m/s, accelerates at 2 m/s2, for 6 sec. How far does the car travel?
(1) LIST (3) Equation
(2) LABEL w/units (4) Solve
mx
x
attVx i
7236362
6*2)6*6(
22
2
Galileo Galilei
1564 - 1642 Galileo formulated the laws
that govern the motion of objects in free fall
Also looked at: Inclined planes Relative motion Thermometers Pendulum
Free Fall
All objects moving under the influence of gravity only are said to be in free fall Free fall does not depend on the object’s original
motion All objects falling near the earth’s surface fall
with a constant acceleration The acceleration is called the acceleration due
to gravity, and indicated by g
Acceleration due to Gravity
Symbolized by g g = 9.81 m/s2
g is always directed downward toward the center of the earth
Ignoring air resistance and assuming g doesn’t vary with altitude over short vertical distances, free fall is constantly accelerated motion
Free Fall – an object dropped
Initial velocity is zero Let up be positive Use the kinematic equations
Generally use y instead of x since vertical
Acceleration is g = -9.81 m/s2
vi= 0
a = g
Free Fall – an object thrown downward
a = g = -9.81 m/s2
Initial velocity ≠ 0 With upward
being positive, initial velocity will be negative
vi 0
a = g
Free Fall - example If a rock is dropped from a
building, and it takes 18
seconds to reach the ground, how tall is the building?
(1) LIST (3) Equation
(2) LABEL w/units (4) Solve
sec18
81.9
??
??
0
2
ts
ma
x
Vs
mV
f
i
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