Hey guys, hah, trying out a new study method here. Its cool cos you can study here while I study. Today, I’m doing physics, on the topic of dynamics. I’m just copying salient parts from the textbook, compiling them into one while listening to beatles on repeat (honestly, I hate the music, therefore I’m listening to it to keep me going). Here goes!
Newton’s first law of motion states that an object at rest will remain at rest and an object in motion will continue in motion at constant speed in a straight line in the absence of a resultany force acting on it.
Balanced forces: No resultant force does not mean that there are no forces acting on the body. It is just that all the forces are balanced.
(gah, ‘Hey Jude’ is disgusting, argh, whatever)
(I can;t stand it!! shut up ratass)
If the forces in an object are unbalanced, there will be a resultant force changing its velocity
A resultant force will cause
-a stationary object to mive
-a moving object to:
Basically its in Newton’s second law, it surmises: Newton’s second law of motion states that the resultant force acting upon an object is equal to the product of the mass and the acceleration of the object; the direction of the force is the same as that of the object’s acceleration.
(which Again (!) is surmised in this formula)
Force= Mass x acceleration
(wow, ‘Yesterday’ is actually quite nice)
In short, we write it: F=ma
(yesterday, love was such an easy game to play, now I need a place to hide away.. hmm.. how melancholic)
On action and reaction: Newton’s third law of motion states that for every action, there is an equal and opposite reaction.
Note to myself: Remember terms free bodies, contact force, gravitational force– important for drawing freebody diagrams!
(doo da doo, let me whisper in your ear..doodadoo)
Friction, friction, the size of the frictional force depend on
-the material in contact
-nature of the surfaces in contact– the rougher the surface the greater is the friction
-is proportional to the force pressing the surfaces together (eg. weight, blah and blahahahha)
-is independent of the area of contact
(Okay, damn, its so bloody easy, there’s like……….one formula to remember?? But the questions are so damnable, can’t do them!)
Mass, weight density
The inertia of an object is the reluctance of the object to change either its state of rest, or if its moving, its motion in a straight line.. greater the masssss, greater its inertia
(hello, goodbye, hello, goodbye.. retarded! LOL I don’t know why you say goodbye I say hell-O (my addition, this word)
Gravitational field is a region in which the mass of an object experiences a force due to gravitational attraction.
Next topic! Whoots!
Turning Effect of forces
(you love me too, say you love me too.. what the. It seemed so easy in the beatles era -.-)
Moment of a force=Force x perpendicular distance from the line of action of the force to the pivot
Nm = F x D
Principle of moment: When an object is in equilibrium, the sum of clockwise moments about any point is equal to the sum of anticlockwise moments about the same point
The centre of gravity is the point through which the entire weight of the object appears to act.
Stable, unstable, neutral equilibrium is understood.
Ways to make a body more stable.
-lowering its centre of gravity
-increasing the area of the base
these 2 conditions together ensure that the vertical line through the centre of gravity of a body falls within its base unless it is tilted by a very large angle. Heavier and broader bases are easier to balance.
Oh, another topic! yay, so productive.
Work, energy, power
Energy is defined as the capacity to do work.
Kinetic energy is the energy a body possesses due to its motion.
Potential energy is the energy stored in an object due to its position, state or shape
Gravitational potential energy is the energy which a body possesses because of its position relative to the ground.
Thermal energy of a body represents the total kinetic energy of athe atoms or molecules in the body.
The principle of conservation of energy states that energy cannot be created or destroyed, but only changes from one form to another.
1/2 mv2 = mgh
1/2 mv(b)2 = mgh(a) + 1/2 mv(a)2
Work is said to be done when a force produces motion
Work = Force x Distance moved in the direction of the force
W= F x d
Power is defined as the rate of doing work.
P (watt/J/s) = W/t = Energy change/t
The internal energy of a body is the combination of the total kinetic energy (due to motion) and potential energy (due to intermolecular forces) of the molecules in the body.
The heat capacity, C, of a body is defined as the amount of thermal energy required to raise the tempertature of the body by 1K or 1 degrees C.
C = Q (thermal energy)/change in temperature. J/K or J/C
The specific heat capacity, c, of a material is defined as the amount of thermal energy required to raise the temperature of a unit mass of the material by 1K or 1C.
c = Q/m x temp. change. J/kgC
Q = Pt = mass x specific heat capacity x temp change = heat capacity x temp change
Melting (reverse process, freezing) is a process whereby energy supplied changes the state of a substance from a solid state to a liquid state, without a change in temperature. The energy that is absorbed without a change in temperature is termed latent heat of fusion (melting) of the substance. When a liquid freezes, this latent head is released without any change in its temperature.
Boiling (reverse process, condensation) is a process whereby energy supplied changes the state of a substance from liquid state to gaseous state without a change in temperature. The energy gained without any rise in temperature at this stage is called the latent heat of vaporisation.When steam condenses, it releases its latent heat of vaporisation.
Factors affecting evaporation:
Energy is needed to change a liquid into gas. Higher temp of liquid, higher avg. kinetic energy, increase rate of evaporation.
2. Area of exposed surface
Liquid molecules have more opportunities to leave the surface of the liquid.
3. Humidity of the surrounding air
Humidity is a measure of the amount of water vapour in the air. If humidity is high, there is a lot of water vapor in the air and liquid vaporisation is supporessed. The more humid, the slower evaporisation takes place.
4. Motion of air
The motion of the air carries away the water vapor formed by evaporation, and brings drier air in contact with the wet clothes surface.
Lower the external pressure, higher rate of evaporation.
6. Nature of liquid
A liquid with a lower boiling point evaporates more rapidly. A liquid that evaporates easily is described as volatile.
Cooling by evaporation explained by the kinetic theory will be touched on sometime later, I got to rush off for something!! I’ll go to the more important stuff first.
Latent heat of fusion is the energy needed to change a substance from solid to liquid without a change in temperature.
Latent heat of vaporisation is the energy needed to change a substance from liquid to gas without a change in temperature.
The whole chunk about latent heat in terms of molecular behavior will be touched on sometime later too.
l (f) = Q/m
l (v) = Q/m
Okay yay!! 5 chapters completed and understood!! Back here tomorrow for more!