DAY 34
HWARM UP
pg 112 #40 & 41 (5min)
(Solutions LINK)
CLASSWORK:
0. Reading Quiz (on paper, at the podium) (7min maximum)
**Today is a big practice day. I will be checking classwork Monday** I'm moving the math practice we talked about to Monday
1. pg 112 #42-44; pg 113 #54 (15min)
Check answers here: LINK1 LINK2 LINK3
2. pg 95 #9-12; 14 (20min)
Check answers here: LINK1 LINK2
3. Read and then copy pg 97 Example Problem #1 into your notes (5min)
4. Use pg 96 and the example from pg 97 to solve #15-17
Homework
I will check your HW that is due today (inertia notes and Stump the Chump questions) Monday, as well as your class work from today.
In addition, solve pg 113 # 59, 60, and 63 for tonight's HW.
GOALS: SWBAT...
Recite Newton's 2nd law
Calculate a force using ΣF = ma
Explain "apparent weight"
WARM-UP/HW Check (pg 97 #16)
0. When called, bring up your HW
1. If an object is accelerating, can its forces be at equilibrium?
2. What can you say about the force vectors (arrows) in an FBD of an object at equilibrium?
3. What is the net force acting on a 1.0kg ball in free-fall?
4. Erika and Xochitl are rollerskating. Erika pushes Xochitl, whose mass is 40.0kg with a force of 5.0N. What is Xochitl's resulting acceleration? (Personal bonus points is you A/ can say "Xochitl" correctly, and B/ know what it means)
Reading Quiz
CLASSWORK:
1. Practicing Newton's 1st law
Complete problems 61-62 from CH4, pg 113
Use GUESS. Show units. Box your answer.
2. Notes: Newton's 2nd Law
Also written as ΣF = ma
How do we measure Weight and Mass?
A balance is a tool that can be used to measure mass, or number of particles. Since all objects accelerate downward at the same rate in a uniform gravity field, a balance can use objects with a known mass and compare them to objects of unknown mass.
A spring scale is a tool that measures force. A certain force will always stretch the spring the same distance. Because gravity is a force that is relative to position, a spring scale will not always register the same force for an object with the same mass. Moving an object from the surface of Earth to the surface of the Moon, for instance, will give separate force readings on a spring scale. The force reading on a spring scale due to the pull of gravity is called the weight of an object.
The Force of Gravity
To measure the force of gravity on an object, we will use the equation ΣF = ma. Start by imagining the object falling. Draw a free body diagram for an object in free fall. It should show only an Fg arrow pointing downwards. We also know that any object in free fall near the surface of Earth experiences an acceleration g = 9.8m/s2. Therefor, we can rewrite the ΣF = ma equation as
Fg = mg. This will be very useful for us when using free body diagrams to solve force equations.
3. Practice Problems
Complete CH4 pg 97 15, 17, 18 (18 is a cool, but tricky, problem - watch out!!!)
HOMEWORK:
Due Fri
pg 100 #20
pg 101 #21, 23, 24, 26
WARM-UP: (HW CHECK: pg 104: 28, 29; pg 107: 34, 35, 39. Vector Force Labs Due Now)
Newton's 3rd Review Video: https://www.youtube.com/watch?v=8bTdMmNZm2M
Applying Newton's Third Law.
1. Copy and fill in these two versions of Newton's 3rd Law:
"For every action, there is an _________ and _________ reaction"
"For every force, there is an _________ and _________ f_____"
2. Solve:
When a baseball of mass 0.20kg is dropped, its acceleration toward Earth is equal to g, the acceleration due to gravity. What is the force on Earth due to the ball, and what is Earth's resulting acceleration. Earth's mass is 6.0x1024kg.
CLASSWORK:
1. HW Review
2. Forces Review (solutions below)
HOMEWORK: