PHYSICS MR. BALDWIN REVIEW 10/4/13

1. PHYSICS MR. BALDWINREVIEW 10/4/13 Aim: What have we done so far? Let’s review. Do Now: Please take out your notebooks and make a list of what we have done so far? HOMEWORK: Prepare for TEST on Monday 10/7/13. A brief review sheet will be posted online.

2. Rules of Significant figures. • Scientific and decimal notation • 7 basic Units of measurement • Precision & Accuracy • Order of magnitude • Unit conversions between metric and BEU; between metric • Scalars and vectors • Definition & Components of vectors • Examples of both: Speed, distance, and time are scalar quantities; Velocity, displacement and acceleration are all vectors. • Making line graphs • Constant and accelerated motion. • Freefall Motion • Distance & velocity-time graphs.

3. 7 Basic Units of Measurement In Physics, we will be working in the SI system, where the basic units are kilograms, meters, and seconds (m.k.s).

4. METRIC PREFIXES revised These are the standard SI prefixes for indicating powers of 10. CHECK Can you give any common everyday examples where these prefixes are used?

5. Section Check Question A car is moving at a speed of 90 km/h. What is the speed of the car in m/s? (Hint: Use Dimensional Analysis) • 2.5×101 m/s • 1.5×103 m/s • 2.5 m/s • 1.5×102 m/s

7. Order of Magnitude: Rapid Estimating A quick way to estimate a calculated quantity is to round off all numbers to one significant figure and then calculate. Your result should at least be the right order of magnitude; this can be expressed by rounding it off to the nearest power of 10. Section Check Calculate approximately how many basketballs (diameter = 75cm) can fit in this classroom randomly AND orderly stacked one atop the other?

8. Accuracy & Precision • Accuracy: • How close you are to the actual value • Depends on the person measuring • Calculated by the formula: % Error = (YV – AV) x 100 ÷ AV Where: YV is YOUR measured Value&AV is the Accepted Value • Precision: • How finely tuned your measurements are or how close they can be to each other • Depends on the measuring tool • Determined by the number of significant digits

9. Components of Vectors If the components are perpendicular, they can be found using trigonometric functions.

10. Addition of Vectors: Resultant For vectors in same or opposite direction, simple addition or subtraction are all that is needed. You do need to be careful about the signs, as the figure indicates.

11. Recall • Graphs are made using pairs of numbers (x,y). • independent variables are plotted on the x-axis. • dependent variables are plotted on the y-axis. • Range isthe difference between smallest and largest value for a variable • Scale determined by dividing the range by the number of data points and rounding off to the nearest integer. • Titles must be give to graph &placed on both axes

12. Uniform & Accelerated Motion • Uniform motion refers to motion that has a constant velocity • Speed & direction remains the same • Such as your car on cruise control • Moving at 50 mph on a straight road • Accelerated motion refers to motion with changing velocity • As you round a curb • Hit the gas or brake

13. Average Speed & Instantaneous Speed • The instantaneous speed is the speed as given on your speedometer. The speed at that instant. • Speed given by the speedometer • The average speed is the total distance traveled by an object divided by the total time taken to travel that distance. CHECK: Determine the units Unit: m/s; km/h; mph

14. CHECK: Can you write other forms of the equation to determine the other two quantities t & d?

15. Acceleration Acceleration is the change of velocity divided by time. Where a: acceleration; vf: final velocity; vi:initial velocity Determine its Unit. Unit: m/s2

16. Equations of Motion

17. Uniformly Accelerated Motion Galileo’s Law of Freely Falling Bodies: In the absence of air resistance, all objects, regardless of size, shape or mass, fall with the same acceleration.

18. Finding Speed: What can you say about the slope of the graph at any time? The slope of the tangent to the distance-time graph at any point is the instantaneous speed at that point. 8.00 m/s 4.00 m/s

19. Speed-Time Graph of Uniformly Accelerated Motion Slope gives acceleration of the body at each point. Slope 2.00 m/s2 4.00 m/s 2.00 s

20. Graphical Analysis of Linear Motion CHECK How would you find the area under the velocity-time graph? The areabeneath the velocity-time graph gives you the Distance travelled

21. TEST YOURSELF…WHAT DO YOU UNDERSTAND? SCIENTIFIC & DECIMAL NOTATION How do you write a decimal in scientific notation? What is the form? METRIC PREFIXES What are the metric prefixes? What values do the symbols represent? MOTION What is motion? How do you measure motion? SCALARS & VECTORS What is a Scalar? What is a Vector? Give some examples of both scalar and vector quantities. VELOCITY What is Velocity? What is the formula for Velocity? What is the Unit? Is it a Scalar or Vector? ACCELERATION What is Acceleration? What is the formula for acceleration? What is the unit for acceleration?

22. PHYSICS MR. BALDWINNEWTON’S LAWS 10/8/13 Aim: Would a hockey puck sliding on a frictionless ice ever stop? Do Now: What forces are acting on you as you sit in your seat? Homework: “Motion is the rule, not the exception.” Think about this statement. Find some interesting quotes on your own by Isaac Newton.

23. Newton’s First Law The Law of Inertia

24. Laws of Motion: Questions for Thought • What makes something originally at rest begin to move? • Why do some things move faster than others? • Why are some objects accelerated and others not?

25. Question: What Causes an Acceleration? • If a body changes in its state of rest or uniform motion, then it underwent an acceleration. • What caused this? • A force • Simply described as a push or pull on and object. • Thus, a net unbalanced force changes the object’s state of inertia • i.e. state of rest or uniform (constant) motion • A net unbalanced force causes an acceleration • NOTE: A force is not a characteristic of an object. “It is something that one object does to another.”

26. CHECK: What are some examples of force?

27. Newton’s First Law of Motion • Constant velocity is as natural as being at rest. • If you give a ball a push on a frictionless floor, it would move forever. • This conclusion was first reached by Galileo and later stated by Newton as his first law of motion.

28. Newton’s First Law of Motion Newton’s first law is often called the law of inertia. Every object continues in its state of rest, or of uniform motion in a straight line, unless acted upon by an unbalanced (external) force.

29. Examples of Inertia

30. Newton’s First Law of Motion states: If no net unbalanced force acts on it, an object at rest remains at rest and an object in motion remains in motion at a constant velocity (that is at constant speed in a straight line).

31. END. Test your skills • http://phet.colorado.edu/sims/lunar-lander/lunar-lander_en.html

32. PHYSICS MR. BALDWINNEWTON’S 2nd LAW 10/15/13 Aim: Why are some objects accelerated faster then others? Do Now: Is it ever possible for a steel rod and a handful of feathers to have the same mass? Explain. Homework: Worksheet : Newton’s 2nd Law Do Problems 6 - 10

33. What is Inertia? • Inertia is the tendency of an object to resist anychange in its state of rest or uniform motion. What is Mass? • The mass of a body is the property of matter that manifests itself as inertia. • In other words, mass is a measure of inertia.

34. Mass • Mass may be thought of as a quantity of matter contained in an object. • Matter is anything that occupies space • The greater an object's mass, the greater the object's inertia. • The SI unit for mass is the kilogram (kg).

35. Force CHECK. • According to the first law, can an object begins to move all by itself? • No! A force is needed to start it moving. • If an object is moving in a straight line, will it continue to move in a straight line at a constant velocity? • Yes! Unless a force acts to slow it down, speed it up, or changes its direction.

36. Therefore, what can you conclude about a force? • A force is any influence that can change the speed or direction of motion of an object. • A force is any influence that can cause an object to be accelerated.

37. What variables determine whether an object accelerates? • If you push the same chair with two different forces (one small & one large), describe its motion? • What can you conclude about your choice? • If you push a chair and a table with the same force, which one accelerates faster? • What can account for your choice?

38. Newton’s Second Law of Motion Newton’s second law is the relation between acceleration and force. It states, the acceleration of an object is proportional to force and inversely proportional to its mass.

39. Force is a vector • Force is a vector, so . • NOTE: The direction of the acceleration is always in the same direction as the force.

40. Now, Derive the base units of force from the equation. The Newton: The Unit of Force The unit of force in the SI system is the Newton. Unit: 1 N = 1 kg·m/s2 Note that the pound is a unit of force, not of mass.

41. The Newton: the unit of force • The SI unit of force is the Newton (N) • 1 Newton = 1 N = 1 (kg)(m/s2) • The pound (lb) is the unit of force in the British system of measurement • 1 lb = 4.45 N (1 N = 0.225 lb)

42. A force of 1 Newton gives a mass of 1 kilogram an acceleration of 1 m/s2

43. Force The magnitude of a force can be measured using a spring scale.

44. Worksheet: DO problems 1 – 5 • A
car
is
pulled
with
a
force
of
10,000
N.
The
car's
mass
is
1267
kg.
But,
the
car
covers
394.6
 m
in
15
seconds.

 (a) What
is
expected
acceleration
of
the
car
from
the
10,000
N
force?
 (b) What
is
the
actual
acceleration
of
the
car
from
the
observed
data
of
x
and
t?
 (c) What
is
the
difference
in
accelerations?
 (d) What
force
caused
this
difference
in
acceleration?
 (e) What
is
the
magnitude
and
direction
of
the
force
that
caused
the
difference
in
 acceleration?


45. DEFINITIONS • Collinear Forces: forces whose vectors lie along the same straight line. • Concurrent Forces: Forces whose line of action pass through a common point. F1 F3 F2 F3 F1 F2

46. PHYSICS MR. BALDWINNEWTON’S 3rd LAW 10/17/13 Aim: What is the difference between mass and weight? Do Now: QUIZ (8 min) Take out your Newton’s 2nd law worksheet and do #11 on a sheet of paper & turn in. Homework:

47. Effect of Force on Mass: Complete the following statement • When forces of different magnitudes act upon different objects of identical masses, the greater force produces the greater/lesser acceleration. • When the same force acts on objects of different masses, the greater mass receives the greater/smaller acceleration.

48. Friction: just another force • Friction is a force that acts to oppose the motion of an object with which it is in contact. • The harder the objects are pressed together, the stronger the frictional force. • Friction is an actual force, unlike inertia.

49. ??? Question for Thought ??? • An astronaut has a mass of 80 kg on earth. What will his mass be on the Moon? Calculate or Explain. • Describe what would happen to the spring in a bathroom scale if you were on the moon when you stepped on it. How is this different from stepping on the scale on Earth? • http://phet.colorado.edu/sims/mass-spring-lab/mass-spring-lab_en.html

50. Weight – the Force of Gravity Weight is the force exerted on an object by gravity. Close to the surface of the Earth, where the gravitational force is nearly constant, the weight is: