1. Lecture: Covering chapters 1, 2, and 3
Unit 1 Motion and Forces
Lecture:
Covering chapters 1, 2, and 3

2. CHAPTER 1

3. The Scientific Method 6 steps 1. State the problem 2. Research
3. Form hypothesis
4. Test hypothesis
5. Analyze data
6. Draw conclusions

4. Hypothesis A hypothesis is a testable statement It is NOT a question
Ex: My plant will grow taller when it is given milk than when it is given water

5. Experiments Your hypothesis is tested in your experiment
In the experiment you will have an independent variable
As it changes, it affects the dependent variable
Ex: the taller I am (independent) the farther I jump (dependent)

6. Constants and Controls
The variables that do not change in your experiment are called constants
Ex: which melts faster, ice or water?
Constant: flame, container, distance to heat source
A control is what you use to compare your experiment to
Ex: Medicated group compared to the placebo group

7. Theory verses Law Theory Explanation
Has undergone a great deal of testing
Can be changed and adapted as needed
Law
Explains how natural phenomena works
Always gets the same results

8. SI System of Measurement
Length meter m
Mass gram g
Time second s
Temperature kelvin k

9. Common SI prefixes Kilo- 1,000 1 kilogram = 1,000 grams Milli- 0.001
1,000 milligrams= 1 gram
Centi
100 centimeters = 1 meter

10. Converting between units
How many milligrams are in 60 kilograms?
How many centimeters are in 15 millimeters?

11. Volume Volume is the amount of space an object takes up
V= length x width x height
Know that 1mL = 1 cm^3
What is the volume of an object which measures 5cm by 15cm by 20 cm?

12. Density Density is mass divided by volume Mass is measured in grams
Volume is measured in cm^3 or mL
What is the density of an object that weighs 10g and has a volume of 2mL?

13. Kelvin and Celsius Kelvin is the SI unit for temperature
To calculate Kelvin, simply add 273 to the temperature in Celsius
Absolute zero is 0 degrees Kelvin
Absolute zero therefore is -273 degrees Celsius

14. Line graphs vs. Bar graphs

15. Line graphs are used to measure data compared to time
The X axis is time (horizontal)
The Y axis varies (vertical)
Bar graphs are used to compare data
Pie graphs are used to compare percentages

16. CHAPTER 2

17. Distance vs. Displacement
How far an object has moved
I ran 10 meters north and 30 meters south. How far did I run?
Displacement:
How far the object moved from the starting point
What is my displacement in the previous problem?

18. Motion Distance- how far object moved
Displacement- distance and direction the object moved from starting location
Speed = distance / time (Don’t forget units)
Ex: 5 m/s

19. Speed You travel 10 meters in 2 seconds. What was your speed?
Your speed is 100 km/h and you’ve been driving for 5 hours. How far have you driven?

20. Average vs. Instantaneous
Average speed = total d / total t
Instantaneous speed = speed at that given second

21. Trickier problem
Sound travels at 330 m/s. If a lightning bolt hits the ground 1 km away from you, how long will it take for the sound to reach you?

22. Speed vs. Velocity Speed = d / t
Velocity = speed of object and direction of its motion

25. Acceleration
Change in object’s velocity (speed and direction of motion)
Increasing speed =positive acceleration
Decreasing speed = negative acceleration
Acceleration = change velocity / time
Acceleration = (Vf – Vi) / t
Don’t forget units!
Ex: 5 m/s^2
Gravitational acceleration 9.8 m/s^2

26. Acceleration
A jet airliner starts at rest at the end of the runway and reaches a speed of 300 m/s in 20 seconds. Calculate the acceleration.

27. Acceleration again
A skateboarder is moving at a speed of 20m/s and comes to a stop in 2 seconds. Calculate the acceleration.

29. Force Push or pull on an object Gravity is a basic force
Closer objects are together, the grav force between them increases

30. Balanced Force Net force = 0
Same force in opposite directions cancel each other out
No movement

31. Unbalanced Force Unequal forces in opposite directions Movement occurs
Net force = # in one direction
Centripetal force = unbalanced force, with an object accelerating towards the center

32. Inertia Tendency of an object to resist a change in its motion
Newton’s 1st Law of Motion: an object moving at a constant velocity or at rest will remain that way unless it is acted upon by a force
Why should we wear seatbelts?

33. CHAPTER 3

34. Newton’s Second Law of Motion
F = m x a
Force = mass x acceleration
The faster you run into a wall, the more force you exert on that wall
Units are kg m/s^2
Units are Newtons (N)

35. F = m x a
You run into the wall at 50 N of force. Your mass is 10 kilograms. Calculate your acceleration.
Carmine has a mass of 100 g, and he is running toward you at 2 m/s. Calculate the force he will hit you with. (Tricky)

36. Friction
Friction is the force that opposed motion between two surfaces touching each other
There are 3 types:
1. static = not moving
2. sliding = pushing a heavy box across the floor
3. rolling = your car spinning its wheels on the ice

37. Air Resistance
Air resistance affects anything moving in earth’s atmosphere
The amount depends on the speed, size, and shape of the object
Negating air resistance, which will fall faster: a feather or a bowling ball?

38. Terminal Velocity The force of air resistance increases with speed
Remember that the acceleration due to gravity is always 9.8 m/s^2
When the object is falling so fast that it cancels the force due to gravity, it is now at terminal velocity and is no longer accelerating
This is the greatest falling velocity possible

39. Law of Gravitation
Any two masses exert a gravitational force of each other
The size of this force depends on the mass and the distance between the objects
Greater the mass, greater the force
Closer together, greater the force

40. Weight vs. Mass
Weight = mass x acceleration due to gravity (9.8 m/s^2)
Weight is in Newtons
Weight is a force
Mass is in kg
Mass is the measure of amount of matter an object contains

41. Calculating weight
How much does a person with a mass of 70kg weigh on planet Earth?
How much does a baby with a mass of 500g weigh on planet Earth? (Tricky)

42. Projectile Motion
When you throw a ball on Earth, there are two forces working on it
Vertical force pulling down (gravity)
Horizontal force pushing out (your throw)

43. Newton’s Third Law of Motion
For every action there is an equal and opposite reaction
Ex: rocket propulsion

44. Momentum momentum = mass x velocity p = m x v
Law of Conservation of Momentum
Momentum can be transferred from one object to another
Total momentum of the system remains the same

45. Calculating momentum
Compare the momentums of a 50kg dolphin swimming 16.4m/s and a 6,300kg elephant walking 0.11m/s.