Physics Terms

Speed

distance moved per unit time

Velocity

Rate of change of displacement

Acceleration

Rate of change of velocity

Constant acceleration

Constant rate of change of velocity

Free fall

acc = 10 m/$s^2$

velocity = negligible, A.R = negligible

Constant velocity (falling down)

acc = 0, Fr = 0

velocity = max

Newton’s First law

Obj will remain in its state of rest or uniform motion in a straight line, UNLESS a resultant force acts on it

Newtons Second Law

• The resultant force of acting on an obj is the product of its mass and acceleration

• The direction of the resultant force acting on an obj is in the same direction of the acceleration

Newtons Third Law

For every action force (that A acts on B), there will be an equal and opposite reaction force (by B back onto A).

Rules for action-reaction forces

• same nature

• same magnitude

• opposite magnitude direction

• act on diff bodies

Friction

• force that that opposes motion between bodies in contact

• only acts when obj is moving

Fr = 0

• forces acting on an obj are balanced

• acc = 0

• obj is either in constant motion or at rest

Pressure

force acting on obj per unit area

Mass

Measure of amount of substance in an object

Weight

Amount of gravitational force acting on obj

Gravitational field

Gravitational force acting per unit mass

Inertia

• Obj’s reluctance to change its state of motion, due to its mass

• Greater mass = Greater inertia

Pressure

Force acting on obj per unit area

Mass vs Weight

Mass vs Weight

Scalar quantity $\vert$ Vector quantity

Independent of gravitational field strength $\vert$ Dependent on the gravitation field strength

SI unit: kilogram $\vert$ SI unit: Newton

measured w electronic balance $\vert$ measured w spring balance

Principle of moments

For an obj in rotational equilibrium, the sum of clockwise moments about a pivot equals to the sum of moments about the same pivot.

(FOIRE, sCWm = sACWm)

Moment

The product of the force & the perpendicular dist from the LOA of force to the pivot

Center of gravity

The point where the entire weight of an object seems to act on

Line of action

Vertical line which the C.G lies on

Density

Substance’s mass per unit volume

Stability

Ability of an obj to return to its o.g position after being displaced slightly

How to increase stability of an obj?

• increase base area

• lower C.G

Stable equilibrium

• Obj returns to its o.g position after being displaced slightly

• C.G raised slightly

• LOA falls within base area

• creating a restoring moment

• obj returns to o.g position

Unstable equilibrium

• Obj moves to new position after being displaced slightly

• C.G lowered slightly

• LOA falls outside on base area

• creating a toppling moment

• obj moves to new position

Neutral equilibrium

• C.G of obj remains @ same lvl thru out

• LOA cuts thru pivot

• perpendicular dist = 0

• moment = 0

Work done

Product of the force & dist moved in the direction of the force

Energy

Capacity to do work

Conservation of energy

• energy cannot be created nor destroyed

• energy can only be transformed from one form to another

• total amount of energy in an isolated system remains constant

Loss in ____ = Gain in ____

Power

rate of work done

Solid, Liquid, Gas: Arrangement

Solid: very closely packed, fixed regular arrangement

Liquid: closely packed, irregular arrangement

Gas: very far apart, irregular arrangement

Solid, Liquid, Gas: Movement

Solid: vibrate about their fixed positions

Liquid: slide past one another

Gas: randomly moves at high speeds

Solid, Liquid, Gas: FOA

Solid: vry strong

Liquid: strong

Gas: vry weak

Total internal energy

Internal kinetic energy + Internal potential energy

Why no temp change during boiling/melting?

• internal energy is being used to overcome the intermolecular FOA between particles

• ∴ particles’ PE ↑

• while KE remains constant

• ∴ temp stays constant

Why no temp change during freezing/condensation?

• internal energy is being released to form intermolecular bonds between particles

• ∴ particles’ PE ↓

• while KE remains constant

• ∴ temp stays constant

Thermal process: how is energy transferred between 2 regions ykyk

• thermal energy flows from region of higher temp to region of lower temp

• until thermal equilibrium is achieved between the 2 regions

Thermal equilibrium

• state where 2 or more regions have the same temp

• no net transfer of energy between them

Conduction

transfer of thermal energy thru medium w/o any flow of the medium

How does conduction work? (non-metal)

• particles closest to heat source gain internal energy

• they start to vibrate more vigorously + faster

• they collide more frequently w neighbouring particles

• ∴ passing on some of their internal energy to neighbouring particles, causing them to vibrate more too

• this process of increased vibrations & collisions repeats along whole obj