Physics Biology Education

Mechanics

1. Weight (force of gravity) decreases as you move away from the earth by distance squared.
2. Mass and inertia are the same thing.
3. Constant velocity and zero velocity means the net force is zero and acceleration is zero.
4. Weight (in newtons) is mass x acceleration (w = mg). Mass is not weight!
5. Velocity, displacement [s], momentum, force and acceleration are vectors.
6. Speed, distance [d], time, and energy (joules) are scalar quantities.
7. The slope of the velocity-time graph is acceleration.
8. At zero (0) degrees two vectors have a resultant equal to their sum. At 180 degrees two vectors have a resultant equal to their difference. From the difference to the sum is the total range of possible resultants.
9. Centripetal force and centripetal acceleration vectors are toward the center of the circle- while the velocity vector is tangent to the circle.
10. An unbalanced force (object not in equilibrium) must produce acceleration.
11. The slope of the distance-tine graph is velocity.
12. The equilibrant force is equal in magnitude but opposite in direction to the resultant vector.
13. Momentum is conserved in all collision systems.
14. Magnitude is a term use to state how large a vector quantity is.


Energy

15. Mechanical energy is the sum of the potential and kinetic energy.
16. Units: a = [m/sec2], F = [kg•m/sec2] (newton), work = pe= ke = [kg•m2/sec2] (joule)
17. An ev is an energy unit equal to 1.6 x 10-19 joules
18. Gravitational potential energy increases as height increases.
19. Kinetic energy changes only if velocity changes.
20. Mechanical energy (pe + ke) does not change for a free falling mass or a swinging pendulum. (when ignoring air friction)
21. The units for power are [joules/sec] or the rate of change of energy.


Electricity

22. A coulomb is charge, an amp is current [coulomb/sec] and a volt is potential difference [joule/coulomb].
23. Short fat cold wires make the best conductors.
24. Electrons and protons have equal amounts of charge (1.6 x 10-19 coulombs each).
25. Adding a resistor in parallel decreases the total resistance of a circuit.
26. Adding a resistor in series increases the total resistance of a circuit.
27. All resistors in series have equal current (I).
28. All resistors in parallel have equal voltage (V).
29. If two charged spheres touch each other add the charges and divide by two to find the final charge on each sphere.
30. Insulators contain no free electrons.
31. Ionized gases conduct electric current using positive ions, negative ions and electrons.
32. Electric fields all point in the direction of the force on a positive test charge.
33. Electric fields between two parallel plates are uniform in strength except at the edges.
34. Millikan determined the charge on a single electron using his famous oil-drop experiment.
35. All charge changes result from the movement of electrons not protons (an object becomes positive by losing electrons)


Magnetism

36. The direction of a magnetic field is defined by the direction a compass needle points.
37. Magnetic fields point from the north to the south outside the magnet and south to north inside the magnet.
38. Magnetic flux is measured in webers.
39. Left hands are for negative charges and right hands are for positive charges.
40. The first hand rule deals with the B-field around a current bearing wire, the third hand rule looks at the force on charges moving in a B-field, and the second hand rule is redundant.
41. Solenoids are stronger with more current or more wire turns or adding a soft iron core.


Wave Phenomena

42. Sound waves are longitudinal and mechanical.
43. Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher (n) value medium.
44. All angles in wave theory problems are measured to the normal.
45. Blue light has more energy. A shorter wavelength and a higher frequency than red light (remember- ROYGBIV).
46. The electromagnetic spectrum (radio, infrared, visible. Ultraviolet x-ray and gamma) are listed lowest energy to highest.
47. A prism produces a rainbow from white light by dispersion (red bends the least because it slows the least).
48. Light wave are transverse (they can be polarized).
49. The speed of all types of electromagnetic waves is 3.0 x 108 m/sec in a vacuum.
50. The amplitude of a sound wave determines its energy.
51. Constructive interference occurs when two waves are zero (0) degrees out of phase or a whole number of wavelengths (360 degrees.) out of phase.
52. At the critical angle a wave will be refracted to 90 degrees.
53. According to the Doppler effect a wave source moving toward you will generate waves with a shorter wavelength and higher frequency.
54. Double slit diffraction works because of diffraction and interference.
55. Single slit diffraction produces a much wider central maximum than double slit.
56. Diffuse reflection occurs from dull surfaces while regular reflection occurs from mirror type surfaces.
57. As the frequency of a wave increases its energy increases and its wavelength decreases.
58. Transverse wave particles vibrate back and forth perpendicular to the wave direction.
59. Wave behavior is proven by diffraction, interference and the polarization of light.
60. Shorter waves with higher frequencies have shorter periods.
61. Radiowaves are electromagnetic and travel at the speed of light (c).
62. Monochromatic light has one frequency.
63. Coherent light waves are all in phase.


Geometric Optics

64. Real images are always inverted.
65. Virtual images are always upright.
66. Diverging lens (concave) produce only small virtual images.
67. Light rays bend away from the normal as they gain speed and a longer wavelength by entering a slower (n) medium {frequency remains constant}.
68. The focal length of a converging lens (convex) is shorter with a higher (n) value lens or if blue light replaces red.


Modern Physics

69. The particle behavior of light is proven by the photoelectric effect.
70. A photon is a particle of light {wave packet}.
71. Large objects have very short wavelengths when moving and thus can not be observed behaving as a wave. (DeBroglie Waves)
72. All electromagnetic waves originate from accelerating charged particles.
73. The frequency of a light wave determines its energy (E = hf).
74. The lowest energy state of a atom is called the ground state.
75. Increasing light frequency increases the kinetic energy of the emitted photo-electrons.
76. As the threshold frequency increase for a photo-cell (photo emissive material) the work function also increases.
77. Increasing light intensity increases the number of emitted photo-electrons but not their KE.


Internal Energy

78. Internal energy is the sum of temperature (ke) and phase (pe) conditions.
79. Steam and liquid water molecules at 100 degrees have equal kinetic energies.
80. Degrees Kelvin (absolute temp.) Is equal to zero (0) degrees Celsius.
81. Temperature measures the average kinetic energy of the molecules.
82. Phase changes are due to potential energy changes.
83. Internal energy always flows from an object at higher temperature to one of lower temperature.


Nuclear Physics

84. Alpha particles are the same as helium nuclei and have the symbol .
85. The atomic number is equal to the number of protons (2 for alpha)
86. Deuterium () is an isotope of hydrogen ()
87. The number of nucleons is equal to protons + neutrons (4 for alpha)
88. Only charged particles can be accelerated in a particle accelerator such as a cyclotron or Van Der Graaf generator.
89. Natural radiation is alpha (), beta () and gamma (high energy x-rays)
90. A loss of a beta particle results in an increase in atomic number.
91. All nuclei weigh less than their parts. This mass defect is converted into binding energy. (E=mc2)
92. Isotopes have different neutron numbers and atomic masses but the same number of protons (atomic numbers).
93. Geiger counters, photographic plates, cloud and bubble chambers are all used to detect or observe radiation.
94. Rutherford discovered the positive nucleus using his famous gold-foil experiment.
95. Fusion requires that hydrogen be combined to make helium.
96. Fission requires that a neutron causes uranium to be split into middle size atoms and produce extra neutrons.
97. Radioactive half-lives can not be changed by heat or pressure.
98. One AMU of mass is equal to 931 meV of energy (E = mc2).
99. Nuclear forces are strong and short ranged.

From : http://regentsprep.org/ (101 physics Facts)

While we're on the subject of space travel, let's talk about free fall and something that is misleadingly called "weightlessness" As you are reading this, you can probably feel your chair pushing upwards on you with a force of several hundred newtons. If your feet are not touching the ground, this is an upwards force equal in magnitude to your weight (a downwards force). My weight is 680 N downwards, so I know that the force from the chair is about this much, upwards. You can also feel your abdominal muscles holding your abdominal organs in place. These forces and some others give you the sensation of having weight. You do not really sense your weight directly very much, because it is applied homogeneously over your whole body. When the forces from the chair or on your abdominal wall are reduced or zero, you may feel 'weightless'--the feeling you get when a lift starts to accelerated rapidly downwards, or when you go quickly over a peak on a roller coaster. I have put 'weightless' in inverted commas because in these situations, and in an orbiting spacecraft, your weight is virtually normal. Since the moon flights stopped, no human has been far enough from the Earth for his/her weight to be substantially reduced.
The three diagrams below show two situations that produce free fall. In an orbiting spacecraft, the spacecraft and the cosmonaut are both accelerating towards the centre of the earth at the same rate (their centripital acceleration is a_c = v²/r, where v is the orbital speed and r the radius). Their weight is what keeps them in orbit: W = ma_c. Because they are *both* accelerating towards the centre of the earth at the same rate, there is on average no force between the cosmonaut and the spacecraft. This absence of forces from seat, floor, abdominal wall etc is what is commonly but misleadingly called 'weightlessness': the cosmonauts in the space station are not without weight, in fact the have (almost) their usual weight. It's just that they don't feel the force of chairs on their bums and they don't feel their abdomens holding in their organs.

feel their abdomens holding in their organs.

                                  

In the figure in the middle, the cable of a lift (elevator) has broken. Both the lift and its passenger are in free fall, accelerating downwards at g. The passenger no longer feels the force on his abdominal muscles, and so, like the cosmonaut, he might say that he feels 'weightless'. He is not, of course, without weight. His weight is still W = mg. Indeed it is his weight that will probably lead to his death, because his unopposed weight is continuously accelerating him. In figure at right, a NASA airplane (nicknamed the 'vomit comet') cuts the power in its engines and, for about 25 seconds, travels in a trajectory that is nearly parabolic. Both the plane and its occupants accelerate towards the Earth at g: all are in free fall. Astronauts are thus exposed to free fall and obtain brief periods of experience in working in this condition.
Physicists tend to use the word 'weightless' in scare quotes (as I have done here), to make it clear that they are not talking about a situation in which there is no weight. Many physicists prefer to avoid the word altogether and talk instead about free fall.
There are some similiarities between the passenger (mass m) in the lift (let's put it at the equator) and a cosmonaut (mass m) in low Earth orbit. The weight of each is about mg. Both accelerate towards the centre of the Earth at approximately g. The difference is that the spacecraft makes a circle around the Earth in about 90 minutes, whereas the lift makes a circle around the Earth in about 24 hours. The acceleration g is just enough to keep an object in low Earth orbit with a period of 90 minutes. It is far too great for the 'orbit' of the hapless passenger in the lift. If a satellite loses speed, it gradually spirals in towards the Earth. The horizontal speed of the passenger in the lift is so low that his 'spiral' towards the center of the Earth is almost a straight line. (There have been a few approximately's and almosts in the above. If you are interested in the analysis of motion in the rotating frame of the Earth, have a look at the formal analysis of the motion of a pendulum at the Earth's surface.)


from : http://www.phys.unsw.edu.au/

The dimensions of a unit describe what kind of measurement it is. For example inches, miles and meters are all different units but they all mesure length. Simillarly, the kilogram, the gram and the pound (lb) are all different units of mass but they all share the dimension of mass. Conventially, the dimension of a unit is written between square brackets. The fundamental dimensional quantities are [M], [L], [T] and [A] to represent mass, length, time and charge respectively. All other quantities can be derrived in terms of these dimensions. Dimensions are useful to derive formula and as a check on whether formula has the correct form.

Use of Dimensions to Derive Equations

If we have some idea or can make an educated guess as to how one physical quantity relates to another we can use dimensions to derive the form of the equation. As an example, consider the equation for the period of pendulum bob. We might suppose that the period depends on the mass of the bob, the length of the pendulum and the acceleration due to gravity
We can express this as T=m^xl^yg^z. Where x, y and z are as yet undetermined indices.
To find the values of x, y and z we convert the formula into its dimensions. On the left-hand side the dimension of the period is [T], the dimension of mass is [M]^x, the dimension of the length of the pendulum is [L]^y and the dimension of g is [LT^-2].

[T]=[M]^x[L]^y[LT^-2]^z.

Equating left-hand indices with matching dimensions on the right-hand side.

[M]: 0=x
[L]: 0=y+z
[T]: 1=-2z

From this we can deduce that z=-1/2, while y=1/2 and x=1/2

Substituting these values into the original equation we obtain. T=m⁰l^1/2g^-1/2= k(l/g)^1/2. Where k is a constant
of proportionality. Compare this with the equation for the period of a pendulum T=2π(l/g)^1/2. The form of the equation is correct, but it cannot determine the constant of proportionality.

From :http://www.splung.com/

According to Newton's first law, an object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. It is the natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain its state of motion. This is often called the law of inertia.

The law of inertia is most commonly experienced when riding in cars and trucks. In fact, the tendency of moving objects to continue in motion is a common cause of a variety of transportation injuries - of both small and large magnitudes. Consider for instance the unfortunate collision of a car with a wall. Upon contact with the wall, an unbalanced force acts upon the car to abruptly decelerate it to rest. Any passengers in the car will also be decelerated to rest if they are strapped to the car by seat belts. Being strapped tightly to the car, the passengers share the same state of motion as the car. As the car accelerates, the passengers accelerate with it; as the car decelerates, the passengers decelerate with it; and as the car maintains a constant speed, the passengers maintain a constant speed as well.

But what would happen if the passengers were not wearing the seat belt? What motion would the passengers undergo if they failed to use their seat belts and the car were brought to a sudden and abrupt halt by a collision with a wall? Were this scenario to occur, the passengers would no longer share the same state of motion as the car. The use of the seat belt assures that the forces necessary for accelerated and decelerated motion exist. Yet, if the seat belt is not used, the passengers are more likely to maintain its state of motion. The animation below depicts this scenario.

If the car were to abruptly stop and the seat belts were not being worn, then the passengers in motion would continue in motion. Assuming a negligible amount of friction between the passengers and the seats, the passengers would likely be propelled from the car and be hurled into the air. Once they leave the car, the passengers becomes projectiles and continue in projectile-like motion.

Now perhaps you will be convince of the need to wear your seat belt. Remember it's the law - the law of inertia.

From :http://www.physicsclassroom.com/

insider the following two statements. First, your friend tells you, "It pick you up at your place at 7:15." Second. the daily newspaper tells you, 'The ninon will rise tonight at 7:15."

Mile these two time values look the same, they are really very different. You would not be surprised if your friend showed up at 7:10 or 7:20. On the other hand. if the moon peeked over the horizon at 7:16, an astronomer might scion he looking for a job. The magnitudes of these two measurement statements are the same, but their uncertainties are very different.

No measurement is perfect. Consider the measurement of the height of a cylinder, shown in Figure 1-1. The centimeter scale, even if you paid a lot for it, is not perfect. Whoever uses it does not have infinitely perfect eye­sight. It might not he perfectly aligned with the cylinder. and the cylinder might not he perfectly uniform all the way around. These pitfalls in the process of measurement can he reduced. but they can never be completely dim inated. Furthermore, measurements are necessarily inexact because of the nature of the thing being measured. What is the diameter of a tennis balk It is so fuzzy that no sharp boundary exists between the ball and the space it is in. Ultimately, on the atomic scale, all surfaces are hwy.

In scientific work, every measured value must he accompanied by a state¬ment of its uncertainty. The height of the cylinder in Figure 1-1 would be given as 11.4 centimeters t0.I centimeter; the 10.1 centimeter is the limits of uncertainty in the measurement. nit means that the actual height of the cylinder is probably between 11.3 centimeters and 11.5 centimeters. These limits are not absolute but only probabilistic; even the uncertainty has its uncertainty.

If the limits of uncet tainty are t0.1 centimeter, is the measurement highly accurate? It depends. Finding the height of the cylinder within 0.1 centimeters is not difficult. However, in measuring the distance to the moon, an uncertainty of 0.1 centimeter would be an extraordinatv level of accuracy. It would require a lot of complex and expensive equipment. The accuracy of a measurement is its limits of uncertainty compared with the men¬surrment itself

Accuracy is the ratio of the limits of uncertainty to the measurement, usually expressed as a percent. For the measurement of the cylinder, the accuracy (percent uncertainty) is



if the pert tint uncertainty is known, it is simple to find the limits of uncertainty. Just multiply the magnitude of the measurement by its percent uncertainty. For example, what are the limits of uncertainty of a mass mea¬surement given as 232 grams ± 2%?

there are several concepts about the origin of life, namely:

a. Life Originated from the Sea
in the biosphere there are a variety of energy-containing material. matter and energy that comes from the mountain slopes, valleys flowing water washed into the river to the sea eventually.

In a sea of material collected in the form of chemicals in the form of the element carbon, hydrogen, oxygen, and nitrogen. With the bubble solution of these elements and chemical reactions occurred at a certain temperature will generate a protein substance of life. Living substance was then that eventually evolved became a living being. living simplest known viruses.

b. Life Originated from the Air
This theory has been proven Professor Urey helped by his assistant Stanley Miller. The theory is called Urey's theory, and this experiment called Miller's Experiment

Chemical compounds in the top layer of the biosphere when exposed to heat will evaporate. Collected atmospheric steam, hydrogen, nitrogen, oxygen, and carbon. In the event of lightning which is a natural electrical energy, causing vapors were able to touch and there was a chemical reaction. A substance reaction results in the form of the protein. Substance is at a certain temperature conditions will be transformed into a substance that later life evolved into living beings.