# Posts by Elena

Total # Posts: 4,389

physics

Physics

physics

Physics
http://physicsphunhouse.com/physics/ff3.pdf

physics
http://farside.ph.utexas.edu/teaching/302l/lectures/node30.html

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

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 ...

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

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

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

physical sciene
v=gt=9.8•3.8=…

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

physics
PE=mgh h↓ => PE↓ at the ground PE=0

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 ...

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...

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

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

Physics
drawings????

physics
Tsinα=F Tcosα=mg F=mg•tanα T=mg/cosα

Physics
E=hf => Electrons jump from third to first orbit

Physics
F=0 since F=qvBsinα (α=0)

Physics
0.5mgh/t=0.5•10⁵•9.8•30=1.47•10⁷ W N= 1.47•10⁷/100=1.47•10⁵

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...

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...

Physics
Δφ=I₁R₁=I₂R₂=15V

Physics
C=q/U=5•10⁻⁶/1.5=3.33•10⁻⁶ F

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

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...

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

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

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...

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 ???

a=v²/2s = 40²/2•860=0.93 m/s² v= v₀-at v=0 t= v₀/a =40/0.93 =43.01 s.

a=v²/2s v= v₀-at v=0 t= v₀/a

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 = …

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

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)

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

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’

physics
v(max) = v =A•ω=A•2πf f = 2Aπ/v

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

mechanics of materials
J=π(D²-d²)/32 =...

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

physics
t= 2vₒ•sinα/g L=vₒ²•sin2α/g,

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=...

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 ...

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 (...

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 (...

Physics
F=ma=mv²/R m=FR/ v²

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

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

physics
d=sqrt( 4²+5²)=6.4 s=10+4+5=19

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

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

Physical science
F(fr) = μmg

Physics
1. mv²/2=μmgs s=v²/2μg 2. mv²/2=Q=cmΔT ΔT=v²/2c (c=129000 J/kg•C) 3. Q=cmΔT= mv²/2 Q1= cmΔT1=cm•2=… ΔQ=Q1-Q= cm•2- mv²/2 = …

physics
1/do +1/di =1/f f= - 0.6 m (for diverging lens), do= 1.5 m 1/di=-1/do+1/f=-(1/1.5+1/0.6)=2.33 di= - 0.43 m (‘-‘ as the image is in front of the lens) Magnification M= - di/do=0.43/1.5=0.287 h=M•H=0.287•10=2.87 cm

physics
E=mgh1-mgh2=mg(h1-h2)= =0.1•9.8(1-0.8)=0.78 J

Physics
α=180-61.2=118.8° Cosine Law d=sqrt{20.2²+31.3²-2•20.2•31.3•cos118.8°} = =44,7 km Sine Law 31.3/sinθ=44.7/sin118.8° sinθ=31.3 •sin118.8°/44.7=0.61 θ= 37.9°

Physics
g=GM/R² gʹ=GM/(R+H)²= GM/(R+H)²= GM/(4R)²= GM/16R² {GM/R²}/{GM/16R²}=16 =9.8/gʹ gʹ=g/16=9.8 /16=0.61 m/s²

Physical Science
Q=λm=335000•0.1=33500 J

Physics
the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², F=6.673•10⁻⁹ N R=10 m F =G•m₁•m₂/R²= G•4m•m/R²= G•4m²/R² m=sqrt{F R²/4G)=…

Physics
I=q/t => q=It=0.74•10⁻³•4•3600=10.66 C, N=q/e=10.66/1.6•10⁻¹⁹=6.66•10¹⁹

mechanics of materials
D=150 mm =0.15 m d= 120 mm = 0.12 m T=40 kN•m = 40000 N•m. J=π(D²-d²)/32 =... T/J=Gθ/L=τ(min)/r, τ(min) = Tr/J=Td/2J=... T/J=Gθ/L=τ(max)/R, τ(max) = TR/J=TD/2J=...

mechanics of materials
E=210 GPa (210 MPa isn’t correct) t=6 mm=6•10⁻³m R=6 m Maximum bending stress is σ(max) = E•t/2R=210•10⁹•6•10⁻³/2•6=105•10⁶ N/m²

mechanics of materials
τ=T/A=400000/25•10⁻⁴=1.6•10⁸ N/m²

mechanical properties of materials
σ=Eε, W/A= Eε, ε=W/AE, Energy=E ε²/2 = E W²/2A²E²= = W²/2A²E= =(30000)²/2•(1200•10⁻⁶)²•210•10⁹= =1.49•10³ J.

mechanical properties of materials
σ=Eε σ=F/A=4F/πd² ε= ΔL/L 4F/πd²=ΔL/L d=sqrt{4FL/πEΔL} = =sqrt{4•650•0.17/π•210•10⁹•0.015•10⁻³}= =6.68•10⁻³ m

Physics
ε=dÔ/dt = d(NBAcosωt)/dt = = - NBAω sinωt, ε(max) = NBAω => ω=ε(max)/ NBA =45/50•0.4•0.35 =6.43 rad/s

Science; Solar System
http://www.universetoday.com/34577/inner-and-outer-planets/ http://en.wikipedia.org/wiki/Sun

physical science
T=3000 N 1. T(x)=Tcosα = ..... 2. T(y) = Tsinα = …..

Physics
a=mv²/R=? h=gt²/2 t=sqrt(2h/g) = sqrt(2•1.83/9.8)=0.61 s. L=v•t = > v=L/t=2.39/0.61=3.92 m/s a= mv²/R= m•(3.92)²/ 0.486 =… You need mass ‘m’

physics
υ=2.2 mol, N₀=6.022•10²³ mol⁻¹, k=1.38•10⁻²³ J/K KE(ave) = υ•N₀•3kT/2 KE(bullet)=mv²/2 υ• N₀•3kT/2= mv²/2 T= mv²/3k• υ• N₀= =7.7•10&#...

physics
Fig.1: path difference Δ₁=0, since distances between each loudspeaker and point O are L For constructive interference Δ₁=2kλ/2=kλ (k(min)=0) => Δ₁=0. Fig.2: path difference Δ₂=L√2 – L= L(√2 –1)= 0....

math
0.85(0.8x)=0.68x => - 32% 1.25(1.4x)=1.75x = > +75%

Physics
h=gt²/2

physics
h=1.8 m, H=6 m, v=7 m/s u=? x is the distance of man to lamp post, y is the distance from the tip of the shadow to the lamp post. From the similar triangles H/h = y/(y-x), 6/1.8 = y/(y-x), 6y -6x=1.8y, 4.2 y=6 x, 0.7y=x, d{0.7y}/dt=dx/dt, 0.7(dy/dt)=dx/dt, 0.7u =v, u=v/0.7=7/0...

physics
Take the ring of the radius ‘r’ and the width ‘dr’ on the disc. The electric field at the distance ‘x’ from the center of the disc is dE=x•dq/4πε₀• {sqrt(r²+x²)}³, where dq=σ•dA = σ•2&#...

Physics

Physics

Physics
F=k•q₁•q₂/r² k =9•10⁹ N•m²/C²

pHYSICS
R(smaller) =r R(larger) = R in series: 1.99(R+r)=12 . ... ..(1) in parallel: 1/R +1/r=1/R₀ R₀=rR/(R+r) 10.7 R₀=12 10.7•rR/(R+r)=12 …..(2) Multiply (1) by (2) 1.99• (R+r)•10.7•rR/(R=r) =144 r=6.76/R …… (3) From (1) R+r=6.03...

math liberal arts
5600/0.4•1.358=10309.3 USD

Math
x=x₁+x₂= 1000sin60 =100sin20= =1000(sin60+sin20)= =1000(0.866+0.342)=1208 feet

math
M-3=±11 M₁₂=14 M₂ =-8

physics
V=V1-V2= πR²h-πr² h=πh(R²-r²) m=ρV=ρπh(R²-r²)

Physics
F=qvBsinα F1=q(v/2)(2B)sinα = qvBsinα = 1.2x10^-3 T

Physics
The object is at the earth's surface.

Physics
F=qvBsinα F1=q(v/2)(2B)sinα = qvBsinα = 1.2x10^-3 T

physics
http://en.wikipedia.org/wiki/Thermal_resistance

Physics
v = sqrt(TL₀/m)= =sqrt(540•0.9/0.0038) =357.6 m/s. Fundamental frequency f: λ=v/f=2L f=v/ λ=v/2L=357.6/2•0.62 = 288.4 Hz. f1=v/λ₁=v/L=357.6/0.62=576.8 Hz f2=v/λ₂=v/(2L/3)=3 v/2L=865.2 Hz

phy
KE(tr) =3kT/2= .... k=1.38•10⁻²³ J/K, T=273+27=300 K.

phy
ΔS =ΔQ/T= cmΔT/T = =600•0.5•280/20=4200 J/K

phy
ΔQ=ΔU+W ΔU = ΔQ – W = =c•m•ΔT + r•m – p•ΔV= = c•m•ΔT + r•m – p{V- (m/ρ)} = =4190•2•10 +2.26•10⁶•2 – 101325(3.3 – 2/1000) = 4515630 J

phy
R=kσT⁴ = 0.92•5.67•10⁻⁸•3000⁴=… W/m² R=P/A => P=AR= A•kσT⁴ = =8•10⁻⁶•0.92•5.67•10⁻⁸•3000⁴= 33.8 W

phy
surface tension

phy
Q = rm= 2•10⁶•1.5=3•10⁶ J t=Q/P= 3•10⁶/2•10³=1500 s=25 min=0.42 h

phy
F₁=kx₁ F₂=kx₂ F₁/F₂=x₁/x₂ x₂=x₁F₂/F₁=…. New length is L+ x₂=…

phy
F=kx=k(L-L`) k=F/(L-L`) W=kx²/2= F (L-L`)²/2(L-L`)= F (L-L`)/2.

Physics
α=(90-24)+ 37=103⁰ Cosine law: d=sqrt{ 41²+33²-2•41•33•cos103⁰}=58 km Sine law: 33/sinβ=58/sin α sinβ= sin α•33/58=0.554 β=sin⁻¹0.554=33.7⁰ angle=33.7⁰-24⁰=9.7⁰ (north of...

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