1. April 25, 2018 Mental Math…be ready. You need:
Clean paper (2) / pencil
Simple machines – lab and foldable
Warm Up:
Mental Math…be ready.
I CAN: demonstrate knowledge of friction.
I CAN: investigate simple machines.

2. Today’s agenda Mental Math Reminders/calendar
Review speed, magic triangle, acceleration.
Lab/notes

3. April 2018 Cougar Mountain! HR 12:10 QUIZ 1 2 No School 3 4 5 6 7 8 14
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday 1
Easter 2
No School 3 4 5 6 7 8
9 F/M – review, metrics
10 F/M- KE vs. PE
Ramp and marble lab
11 F/M- Bal/un forces
Rope, shoes, magnet
12 F/M-
Friction, mass, gravity
*challenge, quiz
13 F/M- Motion and graphing
Story analysis, create the graph. 14 15
16 F/M –
Graph review
Benchmark
17 F/M/E
18 F/M/E
Graphs
19 F/M/E
Force/friction
20 F/M/E 21 22 23
Forces and energy
Work and Simple machines 24
Work and simple machines
QUIZ 25
Mech.adv.
HR 12:10 26
Mech. Adv. 27
Mech. Adv
Cougar Mountain! 28 29 30
Magnets

4. Swagrrr EOG testing May 2018 1 2 3 4 Review Test Assess 5 6 7 8 9 10
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday 1
Forces and energy
Magnets / eclectricity 2
Electricity 3
Catch up 4
Review
Test Assess 5 6 7
Atmosphere 8 9 10 11 12 13
Mother’s Day 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
No School
Memorial Day 29 30 31
Swagrrr
EOG testing

5. June 2018 EOG testing Busch Gardens NCFE testing 1 2 3 4 5 6 7
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday 1
Atmosphere 2 3 4 5 6 7
8 Last day (due to snow) 9
EOG testing
Busch Gardens
NCFE testing

6. How can we describe motion?
REVIEW
How can we describe motion?
Motion can be described by:
DISTANCE (length)
TIME (min, seconds)
SPEED (distance and time)
DIRECTION (which way)
ACCELERATION (change in motion)
Speed up, slow down, change direction
VELOCITY…speed and direction

7. D S T Speed = Distance Time Time = Distance Speed
REVIEW
The magic triangle of magic-ness!!
Speed = Distance
Time
Time = Distance
Speed
Distance = Speed x Time D S T

8. Graph patterns

9. Speeding Up
Slowing down

10. FORCES Forces may WORK TOGETHER or OPPOSE each other.
When 2 or more forces act on an object, the forces combine to form a net force.
Forces may WORK TOGETHER
or OPPOSE each other.

11. MEASURING FORCE The strength of a force is measured in NEWTONS.
The symbol is (N).
We use a SPRING SCALE to measure force.

12. Shoe lab Now…what if you tried it using a different surface?
Try sand paper (80 grit AND 220 grit), copy paper, foam paper, wax paper.
Hypothesize first!!!

13. COMBINING FORCES = 5 N right + 10 N right 5 N right
Two forces in the same direction can add together to produce a larger net force.
5 N
right + =
10 N
right
5 N
right

14. COMBINING FORCES = 5 N right - 5 N left 10 N left
Two forces in opposite directions can subtract to produce a smaller net force in the direction of the larger force.
5 N right - =
5 N left
10 N left

15. COMBINING FORCES 0 N = - 5 N right 5 N left
Two forces may cancel each other out (if equal and opposite) to produce NO NET FORCE.
5 N right
5 N left - =
0 N
(No Net Force)

16. Review of Friction Forces

17. Review - What is Friction?
Friction is a force that two surfaces exert on each other when they rub against each other.
The direction of the friction force is always OPPOSITE to the direction of the motion.
It SLOWS down moving objects!
Direction of Motion
Friction Force

18. & AIR RESISTANCE The physics of falling
GRAVITY
& AIR RESISTANCE
The physics of falling

19. The Force of Gravity
Gravity is the force that pulls all objects down to the earth.
Rain falls from the sky down to earth…
If you drop a book, it falls to the ground…
If you trip, you’ll fall down…

20. Universal Gravitation
Actually in science, gravity is a force of attraction that acts between ALL objects (the earth, you, the desk, a book)
The force of gravity is much STRONGER for LARGER objects (more mass).

21. Universal Gravitation
Because the Earth is by far, the largest and closest object around, it has the greatest force of attraction...
So, no matter where you are on earth, all things fall to the ground due to gravity…

22. What is “free fall”?
When gravity is the ONLY force acting on an object, it is in free fall.
In that case, gravity is an UNBALANCED FORCE which causes the object to accelerate.

23. Acceleration due to Gravity
Calculate the acceleration of an object in free fall.
A = Final speed – initial speed
time
A = 50 m/s – 0 m/s
5 s
Acceleration = 10 m/s2

24. Objects in Free Fall Do all objects fall at the same rate?
If we dropped a bowling ball and a tennis ball from the same height, which would land first?

25. Question: How does mass affect the speed of a falling object?
Mass and Gravity
Nov. 15, 2017
Question: How does mass affect the speed of a falling object?
Hypothesis: (What do you think will happen AND WHY?)
Observations & Data Collection:
Repeat each trial twice and record your observations.
Ping pong ball vs. Wooden ball:
Wooden ball vs. Metal ball:
Ping pong ball vs. Metal ball:
Conclusion: (One sentence)

26. Objects in Free Fall Do all objects fall at the same rate?
ALL objects in free fall travel at the same rate, regardless of mass!
In free fall, heavy objects and light objects fall at the same rate!

27. So, which will land first?
WHY does the penny land first?
Remember the force that opposes motion (slows things down)? FRICTION!
Falling objects experience friction with the air called AIR RESISTANCE that slows them down.

28. Air Resistance
The larger the object (more surface area), the more air resistance.
That’s why parachutes work! The upward force of the air acting on the LARGE parachute slows you down as you fall.

29. Air Resistance Draw a diagram showing the forces…
Gravity
Draw a diagram showing the forces…
Downward force of gravity is same on both.
Upward force of air resistance is greater on the feather.
The net force (down) is greater on the penny.
Net Force on Penny
Net Force on Feather

30. Gravity Review
Gravity is the force that pulls all objects down to the earth.
When gravity is the ONLY force acting, ALL objects accelerate at a rate of 10 m/s2.
Mass doesn’t matter – in free fall, heavy objects and light objects fall at the same rate!

31. Air Resistance Review
Some objects take longer to fall – they are slowed down by FRICTION with the air called AIR RESISTANCE.
The larger the surface area, the greater the force of air resistance pushing up.
Without air resistance, all objects would fall at the same rate…

32. Draw a free body diagram of the sky diver and label ALL the forces.
Gravity = 1000 N
Air Resistance = 800 N
What is the net force?
Air Resistance = 800 N
Net Force = 200 N
Gravity = 1000 N

33. Simple Machines (Making work easier…phew!)

34. Simple Machines Foldable
8 Simple Machine Notes
7 Lever
6 Pulley
5 Wheel & Axle
4 Wedge
3 Screw
2 Inclined Plane
1 Title Tab
Simple
Machines
By John Smith
Line up your papers about 1-2 cm apart
Fold the papers over.
Number and title each flap

35. Simple Machines Foldable
8 Simple Machine Notes
7 Lever
6 Pulley
5 Wheel & Axle
4 Wedge
3 Screw
2 Inclined Plane
Draw & Describe:
A sloped surface connecting a lower level to a higher level.
Examples:
A boat ramp, wheelchair ramp,propeller, ladder/stairs
Simple Machines Foldable
On each tab, draw and describe that type of simple machine.
Then give 2-3 examples.

36. What are MACHINES?
Most people think of complex, technical, or electronic gadgets with motors…, but machines can be much SIMPLER.
A machine is any device that lets you do WORK in an EASIER or BETTER way.
Basically:
Simple machines make work EASIER.

37. How do machines do work?
Machines make work easier by changing 3 things about the FORCE you exert to do work:
AMOUNT OF FORCE you exert
DISTANCE over which you exert
force
DIRECTION in which you exert force

38. What are SIMPLE MACHINES?
There are only 6 basic simple machines that make work easier:
Inclined Plane
Wedge
Screw
Lever
Wheel & Axle
Pulley

39. COMPOUND MACHINES
Compound Machines – are made of combinations of two or more simple machines.
For example, a simple can opener is a combination of 3 simple machines:
Lever
Wheel & axle
Wedge

40. WORK & SIMPLE MACHINES
Simple machines DON’T change the amount of WORK done!
(They change the size, distance or direction of your FORCE!)
WORK IN = WORK OUT*
(*usually machines lose a bit of work due to FRICTION…)

41. INCLINED PLANE
An inclined plane is a flat, sloped surface. It connects a lower level to a higher level.
You use less force over a longer distance to raise a load to a higher level.
Input Force
Output Force

42. INCLINED PLANE: Examples
Ramps (Boat ramps, wheelchair ramps)
Propeller
Ladders/Stairs

43. SCREW
A screw has a “thread” or “groove” wrapped around a central cylinder.
While turning, it converts a twisting force into a forward or backward force.
Input Force
Output Force

44. SCREW: Examples & Uses
Screws can holds things together or lift materials.
Screws
Screw top lids for jars/bottles
Light bulb
Swivel stools/chairs

45. WEDGE
A wedge has slanting slides that meet at an edge – it splits material apart.
It changes force in one direction into a splitting force that acts at right angles to the blade.
Input Force
Output Force

46. WEDGE: Examples & Uses Ax, Knife, etc. Zippers
Used in all cutting machines (to split materials apart)

47. WHEEL & AXLE
The wheel is locked to the central axle – when one turns, so does the other one.
A short powerful force at the axle, will move the wheel’s edge a long distance.
A long motion at edge of wheel, moves the axle with great force.
Output Force
Input Force
Output Force
Input Force

48. WHEEL & AXLE: Examples & Uses
Screwdriver
Windmill
Cars/Bicycles
Rolling Pin
Door Knob
Fan

49. PULLEY
A pulley is a grooved wheel with a rope, used to raise/lower/move a load.
Pulley systems change the direction and/or decrease the input force so you can move heavier loads.
Output
Force
Input Force
Output Force
Input Force

50. PULLEY: Examples & Uses
Cranes
Raising a flag on a pole
Window Blinds
Raising a sail on a boat
Clothesline

51. LEVER
A lever is a bar that pivots or rotates on a point (called a fulcrum).
Levers may change the size, distance or direction of the force.

52. LEVERS: Examples & Uses
First Class Levers:
Scissors, See-saws, Pliers
Second Class Levers:
Staplers, Nutcrackers,
Wheelbarrows
Third Class Levers
Shovels, baseball bats, tweezers

53. Machines make work easier by changing 3 things about the FORCE:
The amount of force
The distance of the force
The direction of the force

54. Machines make work easier by changing 3 things about the FORCE:
The amount of force
(eg. A ramp lets you lift a heavy object with LESS force)

55. Machines make work easier by changing 3 things about the FORCE:
The distance of the force
(eg. A baseball bat lets you move your arms a short distance, but move the end of the bat a large distance).

56. Machines make work easier by changing 3 things about the FORCE:
The direction of the force
(eg. The pulley on a set of window blinds lets you move the blinds UP with a DOWNWARD pull.

57. How do machines make work easier?
In your science notebook, write the following questions:
When you add pulleys to a system what happens to the force you need to do work?
How can we change a lever to make it easier to lift a heavy weight?

58. What is the mechanical advantage of a machine?
A machine’s mechanical advantage is the number of times a machine increases a force exerted on it.
Mechanical = Output Force Advantage Input Force

59. What is the mechanical advantage of a machine?
You exert 10 N of force on a can opener. The can opener exerts 30 N of force on the can. What is the mechanical advantage?
Mechanical = Output Force = 30 N
Advantage Input Force N
Mechanical Advantage = 3

60. What is the efficiency of a machine?
The EFFICIENCY compares:
the work you put IN to
the work the machine puts OUT.
An IDEAL machine is 100% efficient.
INPUT WORK = OUTPUT WORK
In the real world, some input work is always lost due to FRICTION between the moving parts of the machine.

61. What is the efficiency of a machine?
EFFICIENCY = Output Work x 100% Input Work
You mow the lawn with a rusty lawn mower. You do 50,000 J of work on the lawn mower but only 25,000 J go to cutting the lawn. What is the efficiency of the lawn mower?

62. What is the efficiency of a machine?
You mow the lawn with a rusty lawn mower. You do 50,000 J of work on the lawn mower but only 25,000 J go to cutting the lawn. What is the efficiency of the lawn mower?
EFFICIENCY = Output Work x 100% Input Work
Efficiency = 25,000 J x 100%
50,000 J
Efficiency = 50%

63. Try the rest of the practice problems on your own…
Mechanical = Output Force Advantage Input Force
EFFICIENCY = Output Work x 100% Input Work