Transcript Where in the universe is gravity the only force?

Monday November 28, 2011
Warm Up
Write down the most
exciting thing you did
over Thanksgiving Break
Classwork
# 37 Gravity & Motion
Notes
#38 Gravity Questions to
Ponder
Homework
Complete #38
#37 Gravity & Motion Notes
• Velocity changes 9.8 meters per second due to gravitational
force.
• You can calculate the velocity of a
falling object using the formula
1s
9.8 m/s
2s
19.6 m/s
3s
29.4 m/s
v=g●t
g= acceleration
due to gravity
t= fall time
• EX: What is the velocity of the
soccer ball when it falls for 3
seconds?
v = 9.8m/s2 ● 3 s
v = 29.4 m/s
• All objects should fall at the same rate, but air resistance makes this not
happen
• Air resistance is the force that opposes motion of falling objects through air
– Amount of air resistance depends on size, shape and speed
• Terminal Velocity is when the force of gravity equals the force of air
resistance
– Acceleration stops at terminal velocity and you fall at a constant velocity
http://waowen.screaming.net/revision/force&motion/skydiver.htm
• Free Fall – when the only force acting on an object is gravity
– Not possible on earth
Gravity
Gravity
Air Resistance
Force of gravity is
larger than air
resistance so
acceleration is
occuring
Air Resistance
Balanced force
between gravity
and air resistance
No acceleration =
terminal velocity
Sky Diving Adventure!
#38 Gravity Questions to Ponder
• Which item would fall more quickly to the
ground, an acorn or a leaf? Explain why?
• If gravity is the same for all objects on Earth,
why don’t all objects fall at the same speed?
• What is terminal velocity? Is it a good thing or
a bad thing?
• Why does free fall not really exist on Earth?
Tuesday November 29, 2011
Warm Up
Classwork
What is an unbalanced force?
# 39 Orbiting and Projectile
Motion
#40 Gravity & Projectile
Motion Practice
a. Any force acting on an
object
b. A force that changes the
motion of an object
c. A force that stops an
object ONLY
d. A force that moves an
object ONLY
Homework
Complete #40
#39 Orbiting and Projectile Motion
• Free fall – when the ONLY force acting on an object is gravity.
– In all cases on earth there is no free fall b/c of air resistance
– Where in the universe is gravity the only force?
• Free Fall in SPACE causes orbiting
How orbiting works:
1. The planet has inertia, it
Wants to continue in the same direction
2. Gravity pulls the planet toward the
sun
3. The planet keeps trying to continue
With its inertia, but gravity pulls
Creating an orbit
Planet’s
inertia
• Projectile Motion- the curved path an object
follows when it is thrown near the surface of
the Earth
– 2 parts : vertical motion, horizontal motion
– The horizontal motion is from you throwing the ball
– Horizontal motion is parallel to the ground &
remains constant once it leaves your hand
– The vertical motion is perpendicular to the ground.
– Once the ball leaves your hand gravity can pull the
object 9.8m/s2 toward the ground
How does vertical and horizontal motion create a curved path?
#40 Gravity & Projectile Motion
Practice
• Textbook pg 157 # 2-6
• Describe 3 situations where projectile motion
occurs. Illustrate and identify the cause of the
vertical and horizontal motion in 1 of your
situations
Wednesday November 30, 2011
Warm Up
Which of the following
situations shows projectile
motion?
a. A penny falling off a
building
b. A frog jumping from lilly
pad to lilly pad
c. A baseball being thrown
d. Both b & c show projectile
motion
Classwork
#41 Newton’s 1st Law
#42 NFL & Newton’s 1st Law
Homework
Complete #42
Newton’s 1st Laws Notes
Read pg 158 – 160 to answer the following questions on
#41 in Albert
1.
2.
3.
4.
5.
6.
7.
8.
9.
What is Newtons 1st law of motion?
What is part 1 of Newton’s law?
What is part 2 of Newton’s law?
What is an unbalanced force? *you may have to look
back in your notes*
Why doesn’t a softball continue rolling forever when
hit into the outfield?
How is friction related to Newton’s 1st law of motion?
What is inertia?
How is inertia related to Newton’s 1st law?
How are mass and inertia related?
#42 NFL & Newton’s 1ST Law
http://science360.gov/obj/video/70fadaa8-c3d4-4132ba1f-c98be5caeb14
1. Rewrite Newton’s 1st law in the context of football
2. How does a defender act as an unbalanced force?
3. What is a players resistance to an unbalanced
force?
4. How does inertia make an offensive player difficult
to tackle
5. Describe the difference between mass and weight
6. How does mass effect inertia?
Thursday December 1, 2011
Warm Up
Newtons 1st law applies to
a. Moving objects
b. Objects that are not
moving
c. Objects that are
accelerating
d. Both (a) and (b)
Classwork
# 43 Inertia-Rama
#44 Inertia-Rama
Conclusion
Homework
Complete #44
#43 Inertia-Rama!!!
Predict & Discover
Activity
Table cloth magic trick
- Pull a table cloth out from
under cups of water
Coin Shoot
- Shoot a coin at a stack of
11 coins
Drop a ball at a target while
you are running by
What you think will happen
What happened and why