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7. Worlg Energy, Power -
Potentlal energy = mghm: lnass in kg, g: gravity in 9.8 m/s2h: height in m n = speed of light in air or vacuum / speed of light in medium
Speed of light in air or vacuum always = 3 x 108 m/s
n = Real depth i Apparent depth
Kinetic energy =lrm.f m: mass in kg, v: speed in m/s
Total energy = k.e + p.e * energy lost
Work done: J,Forcel N, dist: m speed of sound = distance / time between gun's
in air flush and sound
if no, of claos = n, then no. of echoes = n - l.speed of sound = (2 x dist x no. of echoes) / time
if ys!41[s!gp!s!s, thenspeed of sound : (2 x dist) / time for 1 clap
Using echo methods
?'ffT','"' tt zDSpeed in m/s 5 = T
Gun's flush and
sound method
Power: W, energy: JTime: s
8, Tempeature:
9. Waves:
10. Light:
Xo =valrrr ^f icr- poin*, )1,oor vol*.*funp'l
x 00L
FfF;l
v: speed in m/s, I frequency in Hz1": wavelength in m
v: speed in m./s, d: distance in mt:timeins
anglel=anglerin reflection
i: angle of incidentr: angle of reflection
n=sini/sinrin refraction
n: refractive index of a medium
i, always the angle in the &ifr: always the angle in the mffim
ll. Sound:
1.2. Electricity:
ElectrostaticsNP: Nanyang Poly means Negative PolyhenePC: Personal Computer means Positive Cellulose Acetate
Electricitv
rcr"---lI w=vq
IlV=IR I
I E;\4lp I
lE=VIt' I
lE=v0 I
lP=E/t I
I P=VI I
I r=v2rR I
I r:I'?n I
Q: Charge iC) I: Cunent (A) | time (s)
W: work or energy (J) V:Voltage (V) Q:Charge (C)V: Voltage (V) I:Cunent (A) R:Resistance (O)
E: work or enogy (J) V:Voltage (V) I: Current (A) t: time (s)
P: Power (W) E: work or energy (J) t: time (s)
P: Power (W) V:Voltage (V) I:Cunent (A)P: Power (W) V:Voltage (V) R:Resistance (C))
P: Power (W) I:Cunent (A) R:Resistance (O)
Cost of using electricity = PoJ{eI in kW x time in hou x unit costs
I
Energy in kwh
RI LI A2x_R2 L2 A1
Resistors
In series: R: Rr + Rz + R3 ...,..
In parallel: l/R = l/Rr + l/Rr + l/Rr...
*A
14. Radioactivity
Half life: Remaining amt: (ll2)" x initial amt(=
Resistance of wire 1, R2: Resistance of wire 2Length of wire 1, L2: Lenglh of wire 2Cross sect. area of wire 1, M: Cross. Sect area of wire 2
Don't have toUse this if you arenot ok with this!.
13. Electromagnetic inductionTransformer I
Vs Ns
Vp Np
Pp : P, : IoVo: IrV,
For 100% efficient or idealtranformer
Where n is no. of half lives = total davs / half lives.
Eg: I have $100 initially and half life is 4 days, after 12 days, what is amt left?
Usinq loqic method (recommended)
$100)$s0)$2s)$12.50
lsthalf 2nd half 3'dhalflive-4days live-4 days live-4 days total: 12 days
or
\: Voltage at primary (power source, a.c, supply)Vr: Voltage at secondary (equipment,eg: lamp)No: No. of turns in primary (power source )N,: No. of turns in secondary (equipment)
Ns / Np : Turn ratio
Po : Power at primary (power supply)P, : Power at secondary (equiprnent)
Vo: Voltage at primary (power supply)Io : Current at primary (power supply)Vr: Voltage at secondary (equipment)I, : Current at secondary (equipment)
Usins formula
No. of half lives = total davs / haif lives = 12 I 4 = 3.
Amt left = (%)r x 100 = $12.50.!
su pplY
sofl lron cora
PURE PIIYSICS (for pure physics students)
I 5. Pressure
Pressure=Force/Area
l6: Light
l7: Temperature
Pressurel Pa, Force: N, Area: m2
Pressure ofair or liquid = height x density x gravity
Pressure: Pa. Height: m, Density: kg/m3, gravity: m/s2
P: Pressure(Pa) V: Volume(m3)
n: Refractive index (no unit), c: critical angle, o
Linear Magniflcatlon m = Image height / Object height
or : Image distance / Object distance
Fil'il&l
F".=";l
m: no unit
F;lE4
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tr;1
Q: Amt of heat (J), m: Mass (kg), ??: Change in temp ("C or K)c: specificheat capacity (J/kg"C)
C: Heat capacity (J/"C), m: Mass (kg),c: specificheat capacity (J/kg"C)
I+: Latent heat of fusion (J), m: Mass (kg),16: Specific latent heat of fusion (J/kg)
L,: Latent heat of vapourisation (J), m: Mass (kg),lu: Specific latent heat of vapourisation (J/kg)