Wednesday
August 20, 2014

Posts by Elena


Total # Posts: 4,331

Physics
Beat frequency f =| f1-f2| 242<f<288 f-242=26 288-f=20 f=268 Hz
March 3, 2013

physics
t=s/v=1/0.1•3•10⁸ =3.33•10⁻⁸ s. y=gt²/2=9.8•(3.33•10⁻⁸)²/2=5.44•10⁻¹⁵ m
March 3, 2013

Physics
f=80 Hz, V=150V, R=3200 Ω, C=3.5•10⁻⁶ F ω=2πf =2π•80=160π(rad/s) ω²=1/T² =1/(2π)²LC => L=1/(2π ω)²C= .... X(L) =ωL= ... X(C) =1/ωC= ... tan φ=(X(L) –X(C))/R = ...
March 2, 2013

Physical Science
1B 2C 3A 4C
March 1, 2013

Physics
T=F=mv²/R=mω²R ω=sqrt(T/mR) f=ω/2π
March 1, 2013

PHYSICS
T=F=mv²/R=mω²R ω=sqrt(T/mR) ω = εt t=ω / ε 2πN= εt²/2 N= εt²/4π
February 28, 2013

Physics
W=KE2-KE1=KE2 - mv²/2= =7.14 - 0.67•2.2²/2 = 5.52 J
February 27, 2013

physics
for springs connected in tandem 1/k=1/k1 +1/k2 => k=1200 N/m the stretch is x=mg/k=5.9•9.81/1200 =
February 27, 2013

Physics
The total charge Q=2q=2•3•10⁻⁶ C=6•10⁻⁶ C. The total area of two spheres A=4π(r₁²+r₂²) = 4π•149•10⁻⁴ m² q₁=QA₁/A= 6•10⁻⁶•4πr₁²/A...
February 27, 2013

Physics
(a) C=εε₀A/d Energy=Q²/2C (b) C₁=εε₀A/2d=C/2 Energy=Q²/2(C/2)= Q²/C
February 27, 2013

Physics
r=0.15 m, E< E₀ The dielectric strength of air E₀ =3 •10⁻³ V/m E=q/4πε₀r² => q=4πε₀r²E = 4πε₀r²E₀= = 4π•8.85•10⁻¹²•0.15²•3 •...
February 27, 2013

Physics
E= - gradφ= = - {(δφ/δx)i̅+(δφ/δy)j̅ + (δφ/δz)k̅}= = 2yz• i̅ –(4z-2xz)• j̅–(4y-2xy)•k̅.
February 27, 2013

Physics
E= - gradφ= = - {(δφ/δx)i̅+(δφ/δx)j̅ + (δφ/δx)k̅}= = 2yz• i̅ –(4z-2xz)• j̅–(4y-2xy)•k̅.
February 27, 2013

physics
v=const => a=0 N =F(x)•cosα F(y)•sinα=mg+F(fr) F(y)=(mg+μN)/sinα F=sqrt(F(x)²+F(y)²)
February 27, 2013

Physics
L=vₒ²•sin2α/g, B. 45°
February 27, 2013

physics
http://en.wikipedia.org/wiki/Electric_power
February 27, 2013

Physics
ε₀=8.85 •10⁻¹² F/m ε=5.4 e =1.6•10⁻¹⁹ C A=4.50•10⁻⁹ m² d=1.08•10 ⁻⁸ m U=54.6•10⁻³V C=ε•ε₀•A/d C=q/U ε•ε₀•A/d =q...
February 25, 2013

PLEASE COULD SOMEONE HELP ME OUT Physics
Separation between two wires is b=2Lsinα=2•0.5•sin3⁰=5.23•10⁻² m The mass of 1meter of the wire is m₀=ρπd²/4=2700•3.14•(0.3•10⁻³)²/4=1.9•10⁻⁴ kg where ρ =2700 kg/m&#...
February 25, 2013

Physics ~really need help!~
2. v₁= {-2m₂v₂₀ +(m₁-m₂)v₁₀}/(m₁+m₂)= =(m₁-m₂)v₁₀/(m₁+m₂)= v₂={ 2m₁v₁₀ - (m₂-m₁)v₂₀}/(m₁+m₂)= = 2m₁v₁₀...
February 25, 2013

PLEASE COULD SOMEONE HELP ME OUT
Separation between two wires is b=2Lsinα=2•0.5•sin3⁰=5.23•10⁻² m The mass of 1 meter of the wire is m₀=ρπd²/4, where ρ is the density of Al The force between two wires (per 1 meter) is F=μ₀I²/2π...
February 25, 2013

Physics
B=sqrt{B(x)²+B(y)²} = … F=qvBsinα sinα=sin90=1 => F=qvB = …
February 25, 2013

Physics
Problem #60 http://drjj.uitm.edu.my/DRJJ/Lecture/PHY407/Sample%20problems%20Chap%2021%20Cutnell.pdf
February 25, 2013

Physics
The field of the wire has a magnitude B(wire) = µ₀•I/(2πd) = … B(wire)/B(hor) = tan11⁰ ==> B(hor) = B(wire)/ tan11⁰ =
February 25, 2013

physics
P =I²R R =ρL/A= ρL/πr² P =I² ρL/πr² r=sqrt(I² ρL/πP)=... L=2 m, I=23.8 A, P=2.6 W, ρ= 1.72 x 10 ⁻⁸ Ω
February 25, 2013

physics
R=R₁+R₂+R₃=1.17+2.84+3.65 =7.66 Ω I=U/R = 20.3/7.66=2.65 A P₁ =I²R₁=2.65²•1.17= P₂ =I²R₂=2.65²•2.84= P₃=I²R₃=2.65²•3.65=
February 25, 2013

Physics
I=317 A B=7.69•10⁻³ T B(wire)=B B(wire)=μ₀I/2πa =B a= μ₀I/2πB= =4π•10⁻⁷•317/2π•7.69•10⁻³=8.24•10⁻³ m
February 25, 2013

Physics
A₁=(L/4)² M₁=p₁•B=I•A₁•B=I•L²•B/16=… A₂=(L/16)² M₂=2p₂•B=2I•A₂•B=2I•L²•B/256=…
February 25, 2013

physics
n=4 rev/s angular velocity ω =2πn =8π rad/s linear velocity v= ωR
February 19, 2013

PHYSICS
I've corrected my mistake in the 1st equation V(x) = - v•cos α +u•cosβ = - 190cos25 + 45cos15=-172.2+43.5= -128.7 km/h, V(y)= v•sinα+u•sinβ= 190sin25 + 45sin15= 80.3 + 11.6 = 91.9 km/h, V=sqrt{V(x)²+V(y)²}= 158.1 km/h I ...
February 18, 2013

Physics
V(x) = - v•cos α +u•cosβ = - 190cos25 + 45cos15=172.2+43.5= -128.7 km/h V(y)= v•sinα+u•sinβ= 190sin25 + 45sin15= 80.3 + 11.6 = 91.9 km/h V=sqrt{V(x)²+V(y)²}= 158.1 km/h
February 18, 2013

Physics
v=190 km/h, α= 25°, u=45 km/h, β =15°. V(x) =v•cos α - u•sin β =… V(y)= v•sinα+u•sinβ=… V=sqrt{V(x)²+V(y)²}=... Sine Law: V/sin(α+ β) =u/sinγ Solve for γ. V directed (α+γ...
February 18, 2013

Physics
PE=CU²/2 U=sqrt{2•PE/C}
February 18, 2013

physics
A= 4πr² => r=sqrt(A/4π )= sqrt(1.2/4•3.14)= 0.31 m φ=q/4πε₀r => q= 4πε₀rφ= =4π•8.85•10⁻¹²•0.31•590=2.03•10⁻⁸ C
February 18, 2013

Physics
k =9•10⁹ N•m²/C², q=4.8•10⁻⁶ C m=5.5•10⁻³ kg r=0.88 m PE₁-PE₂=2KE -kq²/r +3kq²/r =2mv²/2 2kq²/r =2mv²/2 kq²/r =mv²/2 v=sqrt( kq²/rm) = =sqrt{9•10⁹•(4....
February 18, 2013

Physics
E= 8.18•10⁴ V/m d=2.2 mm q=0.775 μ C ε (paper)= 2.3 (a) C=q/U E=U/d C=q/Ed = ... (b) ε₀=8.85•10⁻¹² F/m C= ε₀εA/d => A=Cd/ε₀ε=...
February 18, 2013

Physics
Problem #16 http://drjj.uitm.edu.my/DRJJ/Lecture/PHY407/Sample%20problems%20Chap%2019%20Cutnell.pdf
February 18, 2013

physics science
Since v=const, F(motor) =F(fr) P=F•v=680•27 =18360 W
February 18, 2013

Physics !
P=Fv=Fs/t=267•493/9•60 = … Watt
February 18, 2013

Physics
s=at^2/2
February 18, 2013

Physics
p =F/A =(m+M)g/4πr² = (6.3+67.8)9.8/4π(0.024)²= …
February 18, 2013

physics!
m=10000 kg KE=mv²/2= ...
February 18, 2013

Physics help!!
The total range of the arrow is L=vₒ²•sin2α/g =45²•sin100°/9.8 =203.5 m R=150 m > L/2=101.75 m => the arrow is at its descending path The time of the motion to the point of 'arrow-apple' meeting is t₁=R/v(x)=R/v₀(x...
February 18, 2013

PHY
(a) qB =–2.0 µC and qD = +12.0µ C. q=(- 2 + 12)/2 = 5 µC (b) qA = –8.0 µC, qC = +5.0µ C, and qD = +12.0µ C. q=(- 8 + 5+12)/3 = 9/3=3 µC
February 17, 2013

Physics
KE=mv²/2 v=sqrt(2KE/m)
February 17, 2013

Physics
A=0.75 m, m=8 kg, k= 400 N/m ω=sqrt(k/m) = … x=Acosωt v= - Aωsinωt v(max) = Aω KE=mv²/2 =0.5m A²ω²sinωt KE(max) = 0.5m A²ω²
February 17, 2013

physics
http://answers.yahoo.com/question/index?qid=20090929074248AA1Q7sZ
February 17, 2013

Physics
Problem #53 from http://spotcos.com/misc/UW_PHYS_12X_ANSWERS/Chap%2007%20SM.pdf
February 17, 2013

physics
http://answers.yahoo.com/question/index?qid=20100823120701AA5imnA
February 14, 2013

Physics
http://physicsphunhouse.com/physics/ff3.pdf
February 11, 2013

physics
http://farside.ph.utexas.edu/teaching/302l/lectures/node30.html
February 10, 2013

physics
Larger charges have more field lines beginning or ending on them. They allow to estimate the magnitude of the charge => Answer A
February 9, 2013

physics
The 1st law of thermodynamics ΔQ=ΔU+W= ΔU+pΔV For adiabatic process ΔQ=0 => 0=ΔU+pΔV if p=const and ΔV ↑ => ΔU ↓ The internal energy ΔU depends on temperature; and temperature decreases as the kinetic energy ...
February 9, 2013

physics
to throw the wrench in the direction opposite to the satellite and move to the satellite according to the law of conservation of linear momentum
February 9, 2013

arithmetic
a(n) = a₁ +(n-1)d a(6) = a₁ +(6-1)d=12 a(8) = a₁ +(8-1)d=22 a₁ +5d=12 a₁ +7d=22 a₁ = -13 d=5 a(2) = a₁ +(2-1)d= =-13 +5= =-8
February 9, 2013

physics
R+r=100 1/R +1/r =1/24 => (R+r)/Rr=1/24 100/Rr =1/24 rR=2400 Since r=100-R R(100-R)=2400 R²-100R+2400=0 R=40 Ω => r=60 Ω R=60 Ω => r=40Ω
February 9, 2013

physical sciene
v=gt=9.8•3.8=…
February 9, 2013

physics
Mass per unit length m₀ = m/L Velocity in the stretched string is v = sqrt(T/m₀). t=L/v
February 8, 2013

physics
PE=mgh h↓ => PE↓ at the ground PE=0
February 7, 2013

architecture
Describe the differences you observe between the art and architecture of the Early Renaissance (Chapter 8) and that of the High and Late Renaissance. Select an Early Renaissance work of painting, sculpture, and architecture, and compare them to examples from the High or Late ...
February 5, 2013

Physics ASAP!!
Density of wood is ρ₁=600 kg/m³, density of water is ρ₂=1000 kg/m³, m=0.24 kg, M=? The volume of the wooden block is V=m/ρ₁=0.24/600=4•10⁻⁴ m³. Mg+mg=F(buoyancy) Mg+mg= ρ₂•V•g M= ρ₂...
February 4, 2013

Physics
F=ma The downward force on the burning gases from the exhaust is equal to the upward force on the rocket
February 4, 2013

Physics
mv=(m+M)u u=mv/(m+M)=0.045•220/(0.045+5)=1.96 m/s (m+M)u²/2=(m+M)gh h= u²/2g=1.96²/2•9.8=0.196 m
February 3, 2013

Physics
drawings????
February 3, 2013

physics
Tsinα=F Tcosα=mg F=mg•tanα T=mg/cosα
February 3, 2013

Physics
E=hf => Electrons jump from third to first orbit
February 3, 2013

Physics
F=0 since F=qvBsinα (α=0)
February 3, 2013

Physics
0.5mgh/t=0.5•10⁵•9.8•30=1.47•10⁷ W N= 1.47•10⁷/100=1.47•10⁵
February 2, 2013

Physcs
The coordinate of dark fringe is y=(2k+1)Lλ/2d. The width of the central bright fringe= the distance between the first dark fringes is 2y₁=2•(2•1+1)Lλ/2d =3 Lλ/d. The distance between the third dark fringes is 2y₃=2•(2•3+1)Lλ...
February 2, 2013

Physics
The speed depends on the refractive index of the substance n n=c/v 1. vacuum: c=3•10⁸ m/s 2. air n= 1.000293 => v= c/n =3•10⁸ /1.000293 =2.999•10⁸ m/s 3. water n=1.333 => v= c/n =3•10⁸ /1.333 =2.25•10⁸ m/s 4. glass n...
February 2, 2013

Physics
Δφ=I₁R₁=I₂R₂=15V
February 2, 2013

Physics
C=q/U=5•10⁻⁶/1.5=3.33•10⁻⁶ F
February 2, 2013

Physics
The third harmonic =>L=3λ/2 =3v/2f= =3•125/2•170=1.103 m
February 2, 2013

Physics Electricity
Potential of the corner point is φ=2•k•q/a. Potential of the center is φ₀=2•k•q•2/a√2=2•k•q•√2/a. Δφ= φ₀ - φ=2•k•q/a(1-√2)= 2•k•q• 0.41/a. ΔKE=Work...
February 1, 2013

physics
Index of reflection (glass) n=c/v, v=nc, s=vt, t=s/v =s/nc, where c=3•10⁸ m/s.
January 30, 2013

Physics
v=28.2 m/s, L=19.5 m. L=v t => t=L/v=... h= gt²/2= ...
January 30, 2013

Physics
(a) KE(rot) =I ω²/2 I=2MR²/5 ω=2π/24•3600 = ...(rad/ s) Earth’s mass is M = 5.97•10²⁴kg, Earth’s radius is R = 6.378•10⁶ m. (b) Linear velocity of the Earth is v=ωr = 2π• 1.496•10¹¹...
January 30, 2013

Physics ~Conservation of Energy~ part 2
1) a) W=mgh b) PE=mgh c) E(toral) = PE = mgh d) KE= PE=mgh e) mv²/2=mgh v=sqrt(2gh) 2) pendelum ... car ???
January 30, 2013

Physics (As Level) 12 Grade
a=v²/2s = 40²/2•860=0.93 m/s² v= v₀-at v=0 t= v₀/a =40/0.93 =43.01 s.
January 30, 2013

Physics (As Level) 12 Grade
a=v²/2s v= v₀-at v=0 t= v₀/a
January 30, 2013

Physics
c=899 J/kg •◦ C, r= 3.97 × 105 J/kg m=2800•0.0136= 38.08 kg E = Q=cm(660.4-26.2) + r m = …
January 30, 2013

Physics
c₁=2090 J/kg ,c₂ = 4186 J/kg •◦ C, c₃ =2010 J/kg •◦ C. λ = 3.33•10^5 J/kg, r = 2.26• 10^6 J/kg. m=0.058 kg Q= c₁m(1)+ λm +c₂m(100) +rm + c₃m(1) = …(J) 1MJ = 10⁶J
January 30, 2013

Physics ~Conservation of Energy~
a) E(total) =KE+PE=5+10 =15 J b) v=sqrt(2•KE/m)=…(m/s) c) KE1=15 -3 =12 J d) v1=sqrt(2•KE1/m)=…(m/s) e) PE= mgh = 3J h=3/mg=3/2.5•9.8=.... (m)
January 30, 2013

Physics ~Work Kinetic Energy~
a) KE₀=0 b) KE= 300 J c) v=sqrt(2•KE/m)=…(m/s) 2) a)W=mgh=450•0.25 = ... J b) KE(fin) =0 c) v=0
January 30, 2013

Physics
Ice: Q= λm + cm(t-0) = λm + cmt Water Q=cm₁(81-t) λ=3.33•10^5 J/kg . m=0.123 kg m₁ = 1.9 kg c = 4186 J/kg •◦ C λm + cmt= c m₁(81-t) Solve for ‚t’
January 30, 2013

physics
v(max) = v =A•ω=A•2πf f = 2Aπ/v
January 30, 2013

Science
Jupiter's gravity may have been too great http://wiki.answers.com/Q/Why_did_the_asteroid_belt_not_form_a_planet
January 29, 2013

mechanics of materials
J=π(D²-d²)/32 =...
January 29, 2013

physic
F = mv^2/r is centripetal force. Velocity in the stretched string is v = sqrt(T/m₀)=sqrt{TL/m}.
January 29, 2013

physics
t= 2vₒ•sinα/g L=vₒ²•sin2α/g,
January 29, 2013

college physics
A=5•10⁻⁶ mm², Silver: k₁= 420 W/m•K, L₁= 0.3 m, Nickel: k₂=91 W/m•K, L₂=0.12 m, T=? q=? Q/t=q=k•A•ΔT/L Resistance of the silver rod: R₁=L₁/k₁A₁ =0.3/420•5•10⁻⁶=...
January 29, 2013

physics
The length and diameter of the platinum wire used in a thermometer are often chosen so that the resistance of the device at around 0 ºC is 100 ohms. Such a sensor is a called a PT100 sensor, and its resistance changes by approximately 0.4 ohms per degree Celsius. Using a ...
January 29, 2013

Physics
m=6.8•10⁻³ kg, q=0.161•10⁻⁶C, A=0.0155 m², α=30°, Q=? Let’s find the projections of the forces acting on the plastic ball: x-projections: Tsinα =F ……. (1) y-projections: Tcosα = mg ……(2) Divide (...
January 29, 2013

Physics
m=6.8•10⁻³ kg, q=0.161•10⁻⁶C, A=0.0155 m², α=30°, Q=? Let’s find the projections of the forces acting on the plastic ball: x-projections: Tsinα =F ……. (1) y-projections: Tcosα = mg ……(2) Divide (...
January 29, 2013

Physics
F=ma=mv²/R m=FR/ v²
January 29, 2013

physics
For the 1st leg of the run: velocity(ave) = displacement/time= 750/20=37.5 m/s For the total trip: velocity(ave) = displacement/time= 0 speed (ave) = distance/time= 1500/45 =33.3 m/s
January 29, 2013

physics
the same as when it started from rest since Δv=at=Ft/m
January 29, 2013

physics
d=sqrt( 4²+5²)=6.4 s=10+4+5=19
January 28, 2013

physics
d=sqrt(5.4²+18²)=18.8 m tan α=18/5.4=3.33 α=73.3° (south from east)
January 28, 2013

physics
Distance (due north) y =d•sin13°= … Distance (due east) x=d•cos13°= …
January 28, 2013

Physical science
F(fr) = μmg
January 28, 2013

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