# Physics key points for POSTUTME exams

Physics 100 key point for your POSTUTME.

You are welcome to radiant learners hope you are enjoying our post on this blog, today we will be looking at 100 key points in physics that may be useful for your POSTUTME exams and others exams also.

To achieve a great success in life someone needs to be very hardworking and also have determination along with Prayer.

There’s no substitute to hardwork – Thomas A. Edison

That is why you must try as much as possible to very determined and focus.

Now let go into real focus of today.

Please try as much as possible to mastered these keypoint you may need it at any point in time even after your admission, and you may not know which one will definitely come out in your exams.

1. Density of water increase and decrease as the water temperature increase from 0 degree Celsius. The reasons behind this is because when water is heated from 0 degree Celsius to 4 decree Celsius the water molecules bends which resulted into decrease in volume and when volume decrease the density of water increase.
2. Water is more denser between 0 degree Celsius to 4 degree Celsius.
3. Temperature affect the pressure of water, when temperature increase pressure also increase.
• According to this equations when P directly Proportional to T then P=KT K= P/T
4. kinetics Energy aquired by a body due to motion
• When K.E = 1/2MV^2
5. Potential energy is the energy acquired by the body due to vitue Of rest or position.
• P. E = mgh
6. Law of conversation of energy state that energy can neither be create nor destroy but can be transform form to another.
• Mechanical energy to Electric energy.
• Workdone = change in K.E
7. Power is the rate of doing work
• P =work done / time taken (P=mgh/t =FV)
8. Law of universal gravitaion state that anybody in the universal attract other body in the universal with a force that is directly proportional to the product of the masses and inversely proportional to the square root of the distance.
• Given that F is force G is gravitational force M is the mass R is the distance then F = Gm1m2/r2
9. Gravitational potential is the work done in bringing a body of units mass from infinity to the point
• V = -Gm/r
10. The potential of the gravitational becoming decrease as the body is moving closer to the centre of the earth.
11. The maximum P. E depends on the height which increase with angle thita
12. g it’s only depends on the mass of the earth and not on the mass of an object
13. Machine is a devices which allow force to be applied at the end to overcome existing force at the other end.
14. Velocity ratio is the distance move by efforts to ratio of the distance moved by the load
• V.R = s. E/s.L
15. Mechanical Advantage is the ratio of the load to the efforts
• M = L/E
1. In the absence of the friction the work done by the machine must be equal to the work done on machine
2. The velocity ratio of wheel and anxles is R/r
1. Efficiency is the ratio of the work done by the load to the ratio of the work done by the effort
E = W x S / F x S. = Mechanical advantage / Velocity ratio
2. The V.R of the inclined plane is 1/sin¤
3. The velocity ratio of the gear is the number of the teeth of larger are to the number of the teeth of small gear
4. The velocity ratio of screw is 2 thia r / p
5. A machine is a force multiplier when loaf is greater than effort
6. Energy must be conserved in machine when the friction effect is taken to the account, the energy output of the machine is less than the work input by the machine
7. As friction increase in machine the mechanical advantage will decrease.
8. Velocity ratio depends on the part of the machine not friction
9. In the inclined plane the V.R decrease as ¤ increase
10. Efficiency only depends on friction not the slope

### Continuation

1. Elasticity is when a load is applied to the material and it becomes extend which when the load is release it return to it original position.
2. Hooke law state that the provide the elastic limit of an elastic material is not exceed which provided that the extension is directly proportional to the applied force
Mathematics F= ke
When k= force constant and e is the extension and F is the force
3. Elastic limit is the point in which elastic material do not return to it original position after the force have been removed.
4. Yield point is a point in which elastics material yield all it’s elasticity and become plastic.
5. Stress can be define as force applied per unit area.
When f= force A= Area then S=f/A
6. Strain can be define as a ratio of extension to length giving by s = x/l
7. Young modulus is the ratio of stress to strain
Y= stress / strain = f/a/x/l
————-
x/l
8. A work done of a plastic material Is a applied force over and extension
W = 1/2 x F x S. Or W = 1/2 ke^2
1. Monometer is use to measure pressure
2. Barometer is use to measure atmospheric pressure
1. Energy stored in string or elastic material is a elastic potential energy is a work done In stretching the bar, by distance.
E = 1/2 x K x S^2
2. Young modulus depends only on nature of the material from which the will is made.
3. The human fore arm Is a simple machine.
4. Density can be define as mass per unit volume of a substance.
when mass (m) volume (v) density (p) the mathematical p = mass / velocity
5. Pressure is a force extended on the unit area of a surface.
6. Pressure of solid = Force / Area
7. Pressure of liquid = hdg
8. Pressure depends on density and the height of a substance but not on shape of containers.
9. Atmospheric pressure is the weight of air which supplied by unit area of the earth surface.
10. Atmospheric pressure decrease with altitude I.e the atm value on top of mountain is less than sea level.
11. Siphon is substances use to transfer liquid from one container to another at lower level

### Continuation

1. Sphygmometer is use to measure blood pressure.
2. Aneroid barometer did not have mercury.
3. Relative density of a substance is the ratio of density of substance to density of the water.
4. All metal have density greater than 1 while air and several liquid have density less than one.
5. A upthrust is an upward force that a substance experience when is totally or partially immersed in water.
6. Upthrust is cause as a result of difference in pressure between lower level and higher level of a liquid.
7. The molecules of a liquid is held together by cohesive force of attraction.
8. The cohesive force that held liquid molecules make the surface of the water to behave like stretched elastic material.
9. Cohesive is a force of attraction between the surface of sams molecules e.g mercury.
10. Adhesive is a force of attraction that occurs between the surface of different molecules e.g water and glass.
11. If specific gravity of a substance is less than one of will float in water.

### Continuation

60. Important constant

• Thomson cross-section = 6.652 × 10−29 m2
• Permeability of vacuum = μ0 = 4π × 10−7T2·m3·J-1= 12.566370614 × 10−7T2·m3·J-1
• Mass of an electron = 9.1093897 × 10-31kg
• Mass of a proton = mp = 1.6726231 × 10-27kg
• Mass of a neutron = mn = 1.6749286 × 10-27kg
• Avogadro constant = NA = 6.0221415 × 1023mol-1
• Absolute zero temperature = 0 K = −273.15 °C
• Speed of light in vacuum = c = 2.99792458 × 108m·s-1
1. Mercury can be use to measure high temperature because it has high boiling point, but it cannot be use to measure relatively low temperature because it has a high freezing point of -39 degree Celsius.
2. Alcohol cannot be use to measure high temperature but It can be use to measure very low temperature because it has high freezing point of -115 degree Celsius.
3. When substance is heated it expand because of changes in temperature.
4. The expansion of substance especially the expansion of metals can be use in the construction of bimetallic strip.
5. The construction of bimetallic strips process must contain two equal length of metals and must have different liner expansivity.
6. Linear expansivity of a solid can be define as fractional increase in length per degree rise in temperature.
Given that α = L2 – L1/ L2(T2-T1)
7. Area expansivity is the fractional increase in area per degree rise in temperature.
Given that β = A2 – A1 / A2(T2 – T1) x 2
8. Volume expansivity is the fractional increase in volume per degree rise in temperature.
Given that y = V2 – V1 / V2 ( T2 – T1 ) x 3
9. Fire alarm makes use of a bimetallic strip close an electric circuit when temperature exceed a certain can value.

70 The size is of Kelvin and Celsius is the same but the size of Kelvin is 9/5 more than the size of division on the Fahrenheit.

1. Mercury decrease and increase in glass-mercury thermometer when heated.
2. Heat is the movement of molecules of substance when heated or when heat is applied to a substance while temperature is the measure of degree of hotness and coldness of a body.
3. Heat capacity is the quantity of heat requires to change the temperature of a body by 1 Kelvin
Given H= mc
4. Specific heat capacity is the quantity of heat requires to change the temperature of unit mass of body by 1 Kelvin
Given Q = mc(T2-T1)
5. The phase of matter is solid – liquid – gas
6. Sublimation is when solid change directly to gas without passing through liquid phase. eg iodide.
7. The word latent heat means the quantity of heat requires to change the state of a substance without changes in temperature.
Given Q = mL
8. Specific latent heat of fusion is the quantity of heat requires to change the unit mass of a substance from solid to liquid without changing in temperature.
9. Specific latent heat of vaporization is the heat requires to vaporise a unit mass of substance without changes in temperature
10. Vapour pressure is the pressure exerted by a vapour on the liquid surface.
11. Saturated vapour pressure is a point in which the amount of vapour exerted or being formed by a liquid eventually equal to the amount of liquid that Is re-enter the liquid surface.
12. When saturated vapour pressure (SVP) equal to the external pressure liquids boil.
13. Boiling of liquid take place at a specific temperature, and did not depends on the surface area of the liquid.
14. The impurities can affect the boiling point of a substance,
15. Impurities decrease the melting point of mostly all liquid, but impurities increase or decrease the boiling point of a liquid depends on the type of materials or liquids.
16. Also pressure also affect boiling and melting point of substance.
17. When a substance expand when solidify increase the pressure will lower the melting point e.g ice. But when substance is contract when solidify increase in pressure increase the melting point and vice versa.
18. Humidity is the amount of water (mass) present in the amount of volume of air.
19. Relative humidity is the amount of of water present in the unit volume of air at particular temperature.
Given R.H = (mass of water in air / mass of water vapour) x 100%
20. Dew point is the temperature at which mist just start to form as the water is cooled.
21. The pressure of the water vapour in air cannot exceed the SVP
22. Evaporation take place at all temperature and it affects by the surface are of the liquid, the higher the temperature and surface area of substance the higher the evaporation.
23. The average speed of the molecules is a measure of the temperature of the body.
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