Saturday
March 8, 2014

# Posts by elena

Total # Posts: 4,283

physics
Energy =Power x time =680 W/m2 x 1 second =680 Joule/m2 Energy of 1 photone = hf =hc/λ Number of photones =Energy/energy of 1 photon = N=680• λ/hc=680•478•10⁻⁹/6.63•10⁻³⁴•3•10⁸=…

Physics
(a) Torque is M=p⒨•B•sinα p⒨=NIA If M(max) =sin α=1 M(max)=NIAB, I= M(max)/NAB = =40/250•0.12•0.04•1=33.3 A (b) ℰ=-dΦ=-d(NBAsinωt)/dt= =-NBAωcosωt ℰ(max)=NBAω=2πNBAf= =2π•250...

physics
(a) I =cε₀E²/2 =3•10⁸•8.85•10⁻¹²•(7.9•10⁻⁶)²/2=8.2•10⁻¹⁴W/m² (b) P=I•A=I•πD²/4=8.2•10⁻¹⁴•π•2.1²/4=2.84•...

physics
PE=mgh=10•2=20 J. PE->KE

physics
Question????

Physics
The speed at the 5-m level is of the same magnitude on the way up and on the way down=> s=(v²-v₀²)/2g Solve for v₀

Physics 2
tanα=x/L=3.2•10⁻³/9=3.56•10⁻⁴ tanα≈sinα bsinα=kλ b= kλ/sinα=1•530•10⁻⁹/3.56•10⁻⁴=1.5•10⁻³ m

Physics
M=Iε ε=M/I = 22.9/0.168 = 136.3 rad/s² 2πN=2πn₀t + εt²/2 2πn=2πn₀ + εt n₀=0 => 2πN= εt²/2 2πn= εt => t=2πn/ε N= πn²/ε n=sqrt {εN/π}= =sqrt{136....

physics
Δp(rocket)=Δp(gas)= mv=26•182=4732 kg•m/s

Physics
2s=ct s=ct/2=3•10⁸•2.56/2=3.84•10⁸ m

Physics
2s=vt s=vt/2=345•4.4/2=759 m

Physics
t=2s/v=2•150/345=0.87 s

Physics
Speed of sound at 20⁰ v=343.1 m/s λ=v/f=343.1/512 =0.67 m

Physics
M=M(fr) M=p⒨Bsinα sinα=sin90=1, M=NIAB M(fr)=F(fr)R=μF⒩R NIAB =μF⒩R F⒩= NIAB/μR= =425•0.27•3•10⁻³•0.21/0.81•0.011= =8.11 N

Physics
λ=v/f Speed of sound at 20⁰ v=343.1 m/s f=v/ λ=343.1/0.667=517.4 Hz

machanics
A vertical distance covered for t₁=10 s of accelerated motion is h₁=at₁²/2. The speed at this height is v₁=at₁. The distance covered at decelerated motion during t₂=15- t₁=15-10=5 s is h₂=v₁t₂-gt₂²/2. ...

physics
h=at²/2 a=2h/t²=2•0.76/5.2²=0.056 m/s² Two equations for the loads -m₁a=m₁g-T₁ => T₁=m₁(g+a) ….(1) m₂a=m₂g-T₂,=> T₂=m₂ (g+a) ….(2) and the 3rd equation (on the base of Newton&#...

physics
See the Related Questions below.

physics...
v=sqrt(v₁²+v₂²) = sqrt(4+1) =2.236 m/s s=vt=2.236•5=11.18 m

PHYSIcs!!!
h=gt²/2=> t=sqrt(2h/g). s=vt=> v=s/t=s/ sqrt(2h/g)= =20/sqrt(2•2/9.8)=31.3 m/s

simple PHYISCS
h=gt²/2 t=sqrt(2•5/g)=1.01 s

physics
N= mgcosα F(fr)=μN (a) T₁= mgsinα -F(fr) = = mgsinα - μ(s)mgcosα (b) T₂=F(fr) +mgsinα= =μ(s)mgcosα +mgsinα (c) T₃=F(fr) +mgsinα= =μ(k)mgcosα +mgsinα

Physics
R₂= 116 Ω, ℰ=120 V, P₁=20.7 W, The resistance of light buble R₁=? R=R₁+R₂, I=V/R, R₁=P₁/I²=P₁R²/V²=P₁(R₁+R₂)²/V². R₁²+(2R₂ - V²/P₁)R₁+R₂...

Physics
80•110•10⁶•5.9 =5.192•10¹⁰ W=5.192•10⁷ kWh, 5.192•10⁷•0.11=5.71•10⁶ dollars

Physics
ℰ=IR=IρL/A => I₁ρL₁A = I₂ρL₂A L₂=I₁L₁/I₂=2.3•52/2.9=41.2 m

Physics
R=4.9•10⁹ Ω V=68•10⁻³V I=V/R=68•10⁻³/4.9•10⁹=1.39•10⁻¹¹ A I=q/t =Ne/t N=It/e=1.39•10⁻¹¹•0.45/1.6•10⁻¹⁹=3.9•10⁷

Physics

Physics
M=F(fr)•(d/2) =μ•F•(d/2)= 0.15•0.62•1.2•10⁻²/2 =0.000558 N•m

Physics
(a)KE=mv²/2 (b) PE=mgh (c) KE1=KE+PE (d) mv₁²/2= mv²/2+mgh v₁= sqrt(v² +2gh)

CHM 1010
p₁V₁=p₂V₂ p₂=p₁V₁/V₂

Physics-friction problem
ma=F(fr) =μN=μmg a= μg. s=(v₀²-v²)/2a= =(v₀²-v²)/2μg => v=sqrt{v₀²-2μgs}= =sqrt{21.2²-2•0.005•9.8•58.5} = =21.06 m/s. For the 2nd case: s=(v₀²-v²)/2μ₁g= =(21.2...

physics
h=v₀t+gt²/2, gt²+2v₀t-2h=0 Solve for t. v= v₀+gt

Physics - Electric Potential
ΔPE= -Work=-qΔφ= -{(-0.15)•(13-60)} = =-7.05 J

Physics
F=ILBsinα B=F/ILsinα=0.15/67•45•sin51.5⁰=6.35•10⁻⁵ T

PHYSICS
Work =500mgh=500•12•9.8•2=117600 J. You need 117600•100/20 =588000 J 1 kg gives 30•10⁶J, mass of burning fat is 588000/30•10⁶ = 0.0196 kg

Physics
h=at²/2=20•16/2=160 m

Physics
(a) (m₁+m₂)v=m₁v₁+m₂v₂ v₁(a)= {(m₁+m₂)v-m₂v₂}/m₁ (b) (m₁+m₂)v=m₁v₁-m₂v₂ v₁(b)= {(m₁+m₂)v+m₂v₂}/m₁ (c) (m₁+m₂)v=m₁v&...

physics
L=2mvx=2•m•v•(b/2)=2•3•5.41•3.15/2= ...

physics
m₁=m= 70 kg m₃=0.175 kg, v₃=10 m/s Let v₃ be positive and directed to the right 0= - m₁v₁+m₃v₃ v₁=m₃v₃/m₁=0.175•10/70=0.025 m/s (directed to the left) m₃v₃ =(m₂+m₃)v v= m₃...

physics
Q1=Q2+cm•Δt c=(Q1-Q2)/ m•Δt= =(12000-1300)/0.185•(73-22)= =1134 J/kg•℃

Physics
F=qvB sin12⁰ 1.8F=qvBsinφ sinφ/sin12⁰ =1.8 sinφ =sin12⁰•1.8=0.208•1.8=0.374 φ=sin⁻¹0.374=22⁰

Q(gained) =Q(lost) Q(lost) =Q₁+Q₂+Q₃ Q₁ = c₁m(Δt₁)=2020•1•(120-100) = 40400 J Q₂ = Lm=2256000•1= 2256000 J Q₃=c₂m(Δt₂)=4186•1•(100-85) = 62790 J Q(lost) =40400 +2256000+62790 =235919...

Q(gained) =Q(lost) Q(gained) =Q₁+Q₂+Q₃ Q₁ = c₁m(Δt₁)=2020•1•(120-100) = 40400 J Q₂ = Lm=2256000•1= 2256000 J Q₃=c₂m(Δt₂)=4186•1•(100-85) = 62790 J Q(gained) =40400 +2256000+62790 =23...

physics
After the 1st rebounce the speed is v/2, after the 2nd rebounce – v/4, after the third rebounce –v/8, => m(v/8)²/2=mgh₁ v=sqrt(128gh₁) =141.7 m/s mv²/2=mgh h= v²/2g=141.7²/2•9.8=1024 m

math
An elementary school collected a total of 240 cans during a food drive. Grade 3 students collected 1/3 of all the cans grade 4 students collected 52 cans, and the rest of the cans were collected by grade 5 students. How many cans did grade 5 collect? A.28 B.80 C.108 D.188

physics
Assume g=10 m/s². The ball upward motion 0=v₀-gt, t=v₀/g=10/10=1 s. The train motion for time 1 s 0= v-at, a=v/t=5/1 = 5 m/s², the distance s= v t -at²/2 =5•1 -5•1²/2 = 2.5 m

Physics. LAST PROBLEM!!
A small metal ball with a mass of m = 82.5 g is attached to a string of length l = 1.72 m. It is held at an angle of θ = 58.5° with respect to the vertical. The ball is then released. When the rope is vertical, the ball collides head-on and perfectly elastically with ...

physics
y=gt²/2 t=sqrt(2y/g) =sqrt(2•920/9.8)=13.7 s

Physics
mv²/2=qU v=sqrt(2qU/m) R=mv/qB= (m/qB)• sqrt(2qU/m)= R3/R4 = sqrt{ 2Um q₄B²/q₃B²2Um)= =sqrt(q₄/q₃) sqrt(4e/3e)=1.15

Physics
T=t/N=11.8/10=1.18 s ω=2π/T=2π/1.18=5.32 rad/s T=mv²/R=mω²R=0.013•5.32 ²•0.93=0.34 N

physics
s=2.08 m m=0.592 kg R=0.0786 m a is the acceleration of the system (m1+m2) m₁a= T₁ m₂a= m₂g-T₂ Iε=M => mR²•a/2R = (T₂-T₁)R, T₂-T₁= ma/2, a= m₂g/( m₁+m₂+m/2)=... a=v²/2s v=sqrt(2as)=....

physics
s=2.08 m m=0.592 kg R=0.0786 m a is the acceleration of the system (m1+m2)

physics
m₁a= T₁ m₂a= m₂g-T₂ Iε=M => mR²•a/2R = (T₂-T₁)R, T₂-T₁= ma/2, a= m₂g/( m₁+m₂+m/2)=... a=v²/2s v=sqrt(2as)=... ω=v/R=...

Physics
Magnetic field of the current-carring wire at distance b from it is B=1/2πb If B=B(Earth)/3= 5•10⁻⁵/3 T, I=2πbB= 2π•0.3•5•10⁻⁵/3 = …

Physics
x=0.45 m, D=0.12 m, I= 2 A, B=2.1 kG=2100G= 0.21 T μ₀=4π•10⁻⁷ H/m B=μ₀nI = μ₀NI/x N=Bx/ μ₀I The length of the wire L=N•πD= Bx πD / μ₀I= =0.21•0.45•π•0.12/4π...

Physics
r1=r2=3 m

Physics
The speed is v=s/t=186/3=62 km/h <65 km/h He can arrive on time.

Physics
1. g =GM/R² g₁=GM/(R+h)² g₁/g=30/100= GM R²/(R+h)²GM => 0.3= R²/(R+h)² Solve for “h” (Earth’s radius is R = 6.378•10⁶ m) 2. mv²/(R+h)= GmM/(R+h)² v=sqrt { GM/(R+h)}

physics
Tsinα =ma Tcosα =mg tanα=a/g=3.2/9.8 = 0.33 α = 18°

Physics
E =kq/r² (a) E(x) = E₁-E₃=kq₁/r² - kq₃/r² = =9•10⁹{(1•10⁻⁶/0.23²)- (7•10⁻⁶/0.23²)}= -1.02•10⁶ V/m (b) An altitude of a triangle is h=0.46cos30=0.46•0.866=0.398 m E(y) ...

physics
1. Flowrate=A•v=21•0.89 = 18.69 m³/s 2. A₁v₁=A₂v₂ v₂=A₁v₁/A₂=21•0.89/17=1.1 m/s

Math/Physics
Q=55034175 J c(ice)=2060 J/kg•℃ λ=330000 J/kg c(water)=4183 J/kg•℃ Q=Q₁+Q₂+Q₃ Q=c(ice)m(12.15-0)+λm+c(water)m(t-0), Q/m=12.15•c(ice) +λ+c(water)•t. Solve for “t”

physics
R=ρL/A R =4ρL/πd² R₁ =4ρL/ (π4d²- πd²) =4ρL/ 3πd² R₁=R/3

Physics
sinα=R/L=0.3/1=0.3 α=17.45° mv²/R=Tsinα …..(1) mg=Tcosα …..(2) Divide (1) by (2) v²/Rg=tanα v=sqrt(R•g•tanα)= =sqrt(0.3•9.8•0.31)=0.27 m/s ω=v/R=0.27/0.3=0.9 rad/s f= ω/2π=0.9/2•3.14=...

physics impulse
1) p=mv=2•4= 8 kg•m/s 2) KE=mv²/2 3) At elastic collision p= - mv 4) Δp= p1-(-p2) =mv – (-mv)= 2mv 5) p(wall)= Δp=2mv 6) F•Δt=mv F= mv/ Δt

physics
We’ll use Kirchhoff’s Current Law: At any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node. Node: I₁, I₂ and I₁₂ currents: I₁+I₂-I₁&...

Physics
sini/sinr=n2/n1 n2=n1(sini/sinr)=1.45(sin64.8/sin68.0)=...

Ecology
The eﬀect of humans on the environment is more drastic than that of other species because people have a greater ability to 1. adapt to seasonal changes. 2. learn new skills. 3. alter the environment. 4. eat diﬀerent types of food.

Biology
Eutrophication refers to 1. the concentration of a toxic substance in the tissues of organisms. 2. depletion of mineral resources as a result of leaching. 3. the warming of the earth’s surface. 4. the damage to the ozone layer that protects the earth from UV light. 5. nut...

Physics
http://en.wikipedia.org/wiki/Torque

Physics
F=Rmv=140•0.0026•510/60=3.1 N

Physical Science
convection.

Physical Science
convection.

phical science
Neutrinos are almost massless, travel close to the speed of light, and pass through matter almost undisturbed. Photons, on the other hand, have no mass, travel at the speed of light, yet are absorbed and/or reflected even by fairly sparse matter such as gasses. A photon has an...

physics
kx²/2 = mv²/2 v=sqrt(kx²/m)=sqrt(244•16•10⁻⁴/0.099) =...

physics
v₀ = 8.9 m/s m=4.1 kg R = 0.116 m μ=0.34 === F=ma F(fr)=μmg F=F(fr) ma= μmg a= μg=0.34•9.8=3.33 m/s² The torque M=Iε=(2mR²/5)•ε M=F(fr)•R= μmgR (2mR²/5)•ε= μmgR ε= 5μmgR/2mR²= ...

physics
kx²/2=mgh k=2mgh/ x²= 2•0.0961•9.8•0.591/(0.04754)²=...(N/m)

Physics
See my answer to a similar question below under related questions.

Physics
L₁= μ₀N²A/x₁ => x₁=μ₀N²A/L₁ L₂= μ₀N²A/x₂ => x₂= μ₀N²A/L₂ Δx=x₂-x₁=μ₀N²A{(1/L₁)–(1/L₂)}

Physics
Work=mgh==30•9.8•250 =... Power =mgh/t=30•9.8•250/30•60 =...

physics
a(centr)= mv²/R=0.036•36²/1.31 =…

Chemistry
0.25mol of CO are mixed with 0.90mol of H2 and heated to 950 degrees celcius in a 15L flask at equilibrium 0.190mol of H2O were present, what is the concentration of the other reactants and products at equilibrium and what is Kc

Physics 1
The law of conservation of linear momentum 0=mv-MV V=mv/M= 12•7.7/76.9 =1.2 m/s S=Vt=1.2•2•60 = 144.2 m

physics
ω=v/R ω =2πf v/R=2πf f=v/2πR= …

Physics (Algerbra-based)
a(centr) = a•cosα=14.3•cos30=… a(tang)=a•sinα=14.3•sin30=… a(centr)= v²/R, v=sqrt{a(centr) •R}=...

physics
The airplanes have the same speed -true The airplanes have the same velocity-false

Physics

physics
C=Q/V C=εε₀A/d Situation I: The capacitor is disconnected from the battery, => Q=const (a) V=Q/C=Qd/εε₀A d₁=4d=> V₁=Q/C₁=Qd₁/εε₀A=4 Qd/εε₀A=4V (b) U=CU²/2=Q²d/2εε&...

PHYSICS
ΔKE=ΔPE=mgΔh=60•9.8•42 =24696 J

(a) cm₁(80-T)=cm₂(T-27) 2(80-T)=20(T-27) T=31.8 ℃ (b) λ= 330000 J/kg Q= λm=330000•0.1 =33000 J

Physics
Motion of the particle without deflection => F(el) = F mag) qE =qvB B=E/v=2607/6.81•10³=0.38 T For the second particle F=qE-qv₁B v₁=(F+qE)/qB= =1.8•10⁻⁹•3.72•10⁻¹²•2607}/ 3.72•10⁻¹²&#...

Physics
mv²/R=qvB R=mv/qB ΔR=R₂-R₁= =m₂v/qB - m₁v/qB= = v(m₂ - m₁)/qB)= =3•10⁵•(238-235)•1.67•10⁻²⁷/92•1.6•10⁻¹⁹•0.6= =1.7•10⁻⁴ m

Physics
ΔV=VB-VA =kq/r(B)-kq/r(A)= =kq{r(a)-r(B)}/r(A)•r(B). q = r(A)•r(B)•ΔV/k{r(a)-r(B)}= =(3.4-4.5)•45/9•10⁹•3.4•4.5 = = - 9.5•10⁻¹⁰ C

Phyics
ΔQ =4KCal=16747.2 J ΔQ=ΔU+W ΔU=ΔQ-W =16747.2-1000=15747.2 J

physics
ΔPE=A= q •Δφ Δφ= A/q=6.7•10⁻³/1.85•10⁻⁴=36 V

Physics
h= vₒ²•sin²α/2•g = =L•g•sin²α/2•g•sin2α= = L•sinα/4•cos α= =L•tanα/4

Physics
The voltage induced around the Al ring is ΔV=NΔΦ/Δt=Δ(0.5•B•A) /Δt = =0.5•A •ΔB /Δt. B =μ₀nI, ΔB /Δt= Δ(μ₀•nvI)/ Δt, ΔB /Δt= μ₀•n•ΔI/ ...

Physics
F=mg=100•9.8=980 N

Physics
C=q/U C=εε₀A/d q=CU= εε₀AU/d A) q1= εε₀A4V/2d= 2 εε₀AV/d B) q2 = εε₀2A2V/d= 4 εε₀AV/d max C) q3 = εε₀2A V/2d= εε₀AV/d D) q4 = εε₀A V/...

Physics
KE= m•v²/2 => v²= 2•(KE)/m a=v²/2•s =2(KE)/2•m•s = KE/m•s m•a=e•E E= m•a/e = m•KE/e•m•s = KE/e•s = =250•1.6•10⁻¹⁹/1.6•10⁻¹⁹•0.2 = 1250 V/m

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