1. HONORS PHYSICS
Good morning! Please…
• Take out your homework, to be checked
• Answer the warm-up question:
• A baseball is thrown straight down from a building that is 65 meters tall. Its
initial velocity is 3.0 m/s. What will its velocity be right before it hits the
ground?
2. AGENDA:
1. Physics in the News!
2. Finish projectile motion activity
3. Review
4. Review activities
NOTE: Midterm is Wednesday 9:45-11:45
- Bring a book or work to do if you finish the midterm early
• LAST DAY FOR HOT TASK/MIDTERM WILL BE WEDNESDAY.
• **Cheat sheet update***
3. MIDTERM TOPICS
Topics Suggested Study Techniques
1. Conversion, measurement, precision, • Look over all old tests & know how to
accuracy do every problem
2. One-dimensional motion: constant • Go over your notes from each unit –
speed be familiar with concepts
3. One-dimensional motion: accelerated • Re-do problems from the homework &
motion problems from the review sheet
4. Free-fall motion Format:
5. Vectors • 30 multiple choice
6. Projectile motion • 14 problems with multiple parts
7. Forces & Newton’s laws
4. 1.
CONVERSION, MEASUREMENT, PRECISION, ACC
URACY
• Using factor label method to convert numbers
• What are some examples of SI units used in physics? English units?
• What are the significant figures for the following two numbers:
• 0.02003 54300
• What is precision? What is accuracy?
• How to convert between metric units
• Know kilo- to milli-
5. 2 & 3. ONE-DIMENSIONAL MOTION: CONSTANT
SPEED & ACCELERATION
• Graphing motion
• Identifying the information given on an x vs. t, v vs. t, a vs. t graph
• Slope of the lines on the graphs
• Area under the curve
• Solving problems using one-dimensional motion equations
7. 4. FREE-FALL MOTION
• The acceleration of an object in free-fall
• Using motion equations to solve free-fall problems:
• An object dropped from rest
• An object dropped with an initial velocity
• An object thrown straight up in the air that comes back down.
8. 4. FREE-FALL MOTION
• Sample problem: a ball is thrown straight up into the air at 12.0 m/s.
• What is the velocity of the ball at its maximum height? What is its acceleration at
maximum height?
7.4 m
• What is the maximum height that the ball will reach?
• What will be the velocity of the ball after 2.0 seconds? -7.6 m/s
9. 5. VECTORS
• Difference between scalar and vector quantities
• What are some examples of each?
• Breaking vector into its components
• Solving for resultant vectors by adding or subtracting two vectors
10. 6. PROJECTILE MOTION
• Concepts behind projectile motion
• Projectile motion is anything that has an initial horizontal velocity that is under the
influence of free-fall
• X & y dimensions of motion are completely independent of one another
• What happens in the x-direction?
• What happens in the y-direction?
• What is range? At what angle does any object have maximum range?
• Problems with initial horizontal velocity
• Problems with projectiles launched at an angle.
11. 7. FORCES
• Newton’s laws and how they apply in various situations
• What is Newton’s first law? Second law? Third?
• Drawing free-body diagram
• Problems with friction on an inclined plane
• Problems with friction on a level surface
• Problems with a force applied at an angle
• Calculating coefficients of kinetic and static friction.
12. 7. FORCES
• A student moves a box of books down the hall by pulling on a rope attached to the box.
The student pulls with a force of 185 N at an angle of 25.0 degrees above the horizontal.
The box has a mass of 35.0 kg and the coefficient of friction between the box and floor is
0.27. Find the acceleration of the box.
-1.2 m/s2
13. 7. FORCES
• What is the net force on each object?
FN = 10 N
Ff = 3 N Fa = 5 N
Mg = 10 N
FN = 10 N FN = 10 N
Ff = 3 N Fa = 1 N Ff = 3 N Fa = 3 N
Mg = 10 N Mg = 10 N
14. HOT TASK
• What does the normal force do?
4.0 kg
• How can we find the normal in both
situations shown?
15o
15o
15. NEWTON’S ACTIVITIES
• When a constant force is applied to something, should the speed increase? Should it stay
the same?
• Use Newton’s Second law and think about the scooter activity – did speed change as
force was constant? Did acceleration change?
• Explain how Newton’s first law applies in a car when wearing a seatbelt vs. without a
seatbelt.
16. Example: force applied at an angle
Suppose a 10.0 kg box is pulled at an angle of 30.0 degrees with a force
of 50.0 Newtons. F ¹ mg! N
a) Calculate the normal force of the box å FY = 0 ® FN + Fay - Fg = 0
FN + Fay = mg
FN = mg - Fay ® (10)(9.8) - 50sin30
FN = 73N
a) If the block is accelerating at 1.5 m/s/s, calculate the coefficient of friction.
FN Fa = 50 N å Fx = Fnet = ma
Fay = 50sin(30) Fax - Ff = ma
Ff 30
Fax = 50cos(30) 50 cos30 - m FN = (10)(1.5)
mg
43.3- m (73) = 15
m = 0.39
17. EXAMPLE: FORCE APPLIED AT ANGLE
#5 from handout last week:
A 120.0 N force is applied at an angle of 45 degrees to a 40.0 kg box. The coefficient of
friction between the two surfaces is 0.15. Find
(b) The force due to gravity and normal force
(c) The force due to friction
(d) The acceleration
(e) How fast the object is moving in 10.0 sec
(f) How far it will move in 10.0 sec
19. NEWTON’S THIRD LAW
“For every action there is an EQUAL and OPPOSITE reaction.
• This law focuses on action/reaction pairs (forces)
• They NEVER cancel out
All you do is SWITCH the wording!
•PERSON on WALL
•WALL on PERSON
20. NEWTON’S THIRD LAW
• How does this law apply when there is a collision
between two objects, like a train and a truck??
21. NEWTON’S THIRD LAW
This figure shows the force during a collision
between a truck and a train. You can clearly see
the forces are EQUAL and OPPOSITE. To help
you understand the law better, look at this
situation from the point of view of Newton’s
Second Law.
Ftruck = Ftrain
What about mass & acceleration just after collision?
mtruck Atruck = Mtraina train
There is a balance between the mass and acceleration. One object usually
has a LARGE MASS and a SMALL ACCELERATION, while the other has a
SMALL MASS (comparatively) and a LARGE ACCELERATION.
22. N.T.L EXAMPLES
Action: HAMMER HITS NAIL
Reaction: NAIL HITS HAMMER
Action: Earth pulls on YOU
Reaction: YOU pull on the earth
23. NEWTON’S FIRST LAW
Concepts Problems
• What is it? • What type of problems apply?
• An object in motion will remain in
motion, or an object at rest will
remain at rest unless acted upon 4.0 kg
by an unbalanced force.
• Fnet = 0
• What conditions can occur?
4.0 kg
• Object can be at rest
• Object can be in constant motion
at a constant speed
