Download Freefall and Newton`s 2nd Law ppt

9 second freefall… video
How fast is it going at the bottom?
How tall is it?
Newton’s 2nd Law of Motion
F=ma
If the same force acts on two different objects
with different masses, how does the object’s
acceleration (movement away) compare?
Thinking
about
force
change
• If the force acting on an
object goes up, and the
mass doesn’t change, how
does the acceleration
change?
If the same force acts on two different objects
with different masses, how does the object’s
acceleration (movement away) compare?
F=ma
Thinking
about
force
change
F=ma
• If the force acting on an
object goes up, and the
mass doesn’t change, how
does the acceleration
change?
• F = force
– Measured in newtons (N)
• m = mass
units
– Measured in kilograms (kg)
• a = acceleration
– Measured in meters per second
per second (m/s²)
Multiple
forces can
be exerted
on an
object at
the same
time
• acceleration = change in
velocity over time
What is
acceleration
?
a=
𝑣2 − 𝑣1
𝑡
or a =
Δ𝑣
𝑡
Apply Newton’s 2nd Law to
Physics of kicking field goals
Large asteroid impact simulation
What would happen if you jumped
into a well that went all the way
through Earth?
See answer in video
Newton’s 2nd Law of Motion (F=ma)
describes
falling and weight
(Fg = mag)
• Fg = mag
(or W=mg or F = mg)
Weight is
applied
Newton’s
2nd
– Fg = force due to gravity ( or
W=weight)
– ag (or g) = acceleration due
to gravity
• always = 9.8 m/s2 on Earth
• Does a big guy or little guy fall
faster when bungee jumping?
• Fg = mag
(or W=mg or F = mg)
Weight is
applied
Newton’s
2nd
– Fg = force due to gravity ( or
W=weight)
– ag (or g) = acceleration due
to gravity
• always = 9.8 m/s2 on Earth
• Does a big guy or little guy fall
faster when bungee jumping?
They fall at the same speed, as
mass is irrelevant to freefall
speed
Which would fall faster without air
resistance, feathers or a bowling ball? video
Air Resistance and free-fall
• In air…
– A stone falls faster than a
feather
• Air resistance
affects stone less
• In a vacuum
– A stone and a feather will fall
at the same speed.
Free-fall utilizes “g”
The acceleration of
gravity (g) for objects
in free fall at the
earth's surface is 9.8
m/s2.
Galileo found that all
things fall at the same
rate.
Which would land
first, a bullet fired
or a bullet
dropped?
• Each bullet shows its position at seconds
0, 0.1, 0.2,and 0.3
Free-fall
The rate of falling
increases by 9.8 m/s
every second.
Height = ½ gt2
(Height is abbreviated either “y” or “d”)
For example:
½ (9.8 )12 = 4.9 m
½(9.8)22 = 19.6 m
½ (9.8)32 = 44.1 m
½ (9.8)42 = 78.4 m
Free-fall
A ball thrown horizontally
will fall at the same rate
as a ball dropped
directly.
Its velocity can be
calculated by multiplying
the time in seconds by
“g”.
v=gt
Free-fall
A ball is thrown up from a rooftop
1. When would the velocity be
the highest?
2. When is the vertical velocity =
0 m/s?
3. At what two points are the
velocities equal?
• What does this show?
Projectile motion path shape
An object thrown upward at an angle to the ground follows a
curved path called a parabola.
What do you notice about this shape?
Air Resistance and free-fall
– A person in free fall
reaches a terminal
velocity of around 54 m/s
(about 130 mi./hr.)
– With a parachute, terminal
velocity is only 6.3 m/s
Allows for a safe landing
-the terminal velocity for a
cat is 60 mi./hr.
Air Resistance
•
Ideal angle for a projectile
– In a vacuum, maximum distance is at an angle of 45o
– With air resistance (real world), angle is less
• Baseball will go furthest hit at an angle of around 40o, a soccer
ball at about 33o
9 second freefall… video
How fast is it going at the bottom?
How tall is it?
height of a falling object = d
(for distance, measured in meters)
d=1/2gt²
SOLVE:
How fast is it going at the bottom?
How tall is it?
Falling from Space
Joe Kittenger
• In the context of Theory of Relativity
https://www.youtube.com/watch?v=MQ7N6VYKJ8
Felix Baumgartner
• https://www.youtube.com/watch?v=dYw4me
RWGd4
• 8 min, RedBull
• https://www.youtube.com/watch?v=FHtvDA0
W34I
– 2 min., With mission control