Transcript Motion

Motion
Motion
Motion occurs when the distance between two or
more objects changes. This is not as simple as it
sounds. Motion is all relative to a reference point.
You may think that by sitting completely still in
your chair means you are motionless, and you are
if you use the floor as a reference point. If,
however, you use the sun as a reference point, you
would be moving at a speed of over 65,000 miles.
When determining motion, it is important to
determine a reference for your motion.
Speed
Speed of motion is calculated by dividing the
distance traveled by the time taken to travel that
distance.
speed = distance
time
speed = 2,500 miles
6.0 hours
speed = 416.6 miles/hour
If it takes the plane 6.0 hours to travel
2,500 miles from NY to LA, what was
the average speed was it traveling?
Acceleration
Acceleration occurs when an object’s speed
and/or direction changes. If the object slows
down, it is negative acceleration or deceleration.
Initial Speed = 0.0 m/s
Time = 2.0 seconds
Accel
Initial= Speed
4.0 m/s= –0.0
0.0m/s
m/s
2.0
s m/s
Final Speed =
4.0
Time = 2.0 seconds
Accel = 4.0 m/s
2.0 s
Accel = Sf – Si
Accel = 2.0
Time
m/s2
Final Speed = 4.0 m/s
This
means
thatwould
as I was
going
How
fast
I
be
down the rollercoaster, my speed
going
if I continued
was increasing
2.0 m/s everyat
second.
Firstrate
I was of
going 0.0
this
m/s, then after a second, I was
acceleration
going
2.0 m/s. After for
another
second,
I was going
4.0 m/s.
another
second?
On Earth and other planets (or anything that has mass) a
gravitational force pulls on objects towards its surface and
causes it to accelerate. On Earth, the acceleration due to
gravity for all objects regardless of mass is 9.8 m/s2 (Neglect
air resistance). This means that as things are in free fall (on
gravity is acting on it), every second that goes by, the
object’s speed will increase by 9.8 m/s.
t = 0.0 sec.
Acceleration due to
gravity on Earth is
9.8 m/s2!
s = 0.0 m/s
t = 1.0 sec.
s = 9.8 m/s
If the ball has a
mass
t=
2.0 sec.
of 10.0 kg, what is its
weight in Newtons?
s = 19.6 m/s
t = 3.0 sec.
s = 28.4 m/s
A force is a push or a pull. When there are
balanced (equal) forces acting oppositely on
an object, no motion occurs.
50 N
No
Motion
50 N
When there are unbalanced (unequal) forces
acting oppositely on an object, motion results
in the direction of the greater force.
100 N
50 N
Friction is a force that always opposes
motion. Because of this, friction causes
things to slow down. There are different types
of friction such as rolling, sliding, and static
friction. Air resistance is also a type of
friction known as fluid friction.
Less Surface
Contact
Which will hit the
ground first?
Air Resistance
(friction)
Which will hit the
ground first?
In a vacuum,Vacuum (no air)
there’s no air
resistance.
On the Moon
there is no
air
resistance!
Apollo 15
Commander Dave Scott
W = 400 N
W = 300 N W = 300 N
A.R. = 300 N
A.R. = 300 N
A.R. = 400 N
W = 300 N
W = 300 N
W = 400 N
Oh my Gosh,
you
killed Kenny!
Forces
You Balanced
Kick
Forces!
Butt!
Projectile Motion
A projectile is a moving object that is
not being propelled. (Gravity may be acting
upon it)
Examples: a baseball after it has been
thrown, a rocket after the engines have been
turned off, an arrow after it has left the bow
In projectile motion, horizontal motion and
vertical motion are independent of one
another.
In other words, if Scrat were to jump straight out
for the acorn, his horizontal velocity would remain
the same as each second went by.
But…
His vertical speed would change as gravity
accelerated him downward.
The Acorn is
About to Fall
Get Ready
for the Jump
The Jump Took 3 Seconds.
0
1
2
3
Look closely at the horizontal & vertical distances as each
second passes.
I Love
Projectile Motion
DON’T
A
DROP
CrabbyIT!
Patty !?!
5 meters