DAY 30
11/04/16
#Goals:
WARM-UP:
The team punter is doing some practice... He kicked the ball straight up, at an initial velocity of 14.7m/s. The total flight time of the ball is 3.0s, and the initial height we will call zero.
A. How long does it take the ball to get to its maximum height (ymax)?
B. What is the ball's velocity at ymax?
C. How high does the ball go?
1. List your Givens
2. List your Unknown
3. Choose an Equation
4. Solve! :-)
CLASSWORK
1. Finding ymax practice
pg 74 problem 45
2. CH 3 Test Prep & Review
pg 85 1-9 (your group will be presenting one of these to the class, on the board - be prepared)
ANSWERS:
1. C
2. B
3. A
4. A
5. C
6. C
7. D
8. B
9. D
3. Introduction to Free Body Diagrams (FBD's)
Notes: https://edpuzzle.com/media/57853ae627ed9aaf133db9f3
4. Work time - lab time - test prep time
HOMEWORK
Lab is due Tueday
Exam on CH 3 is Tuesday
Reading Quiz Tuesday on CH 4 pg 87-89
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