Wednesday
July 23, 2014

Posts by Elena


Total # Posts: 4,343

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•10̿...

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)= 0.4...

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
Δφ=2•π•Δx/λ=2•π•0.15/0.65=0.46 π (rad)= =1.45 (rad)

Physics
http://ca.answers.yahoo.com/question/index?qid=20120128195228AAtlh44

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...

science (physics)
Weight = mg m=Weight/g=3920/9.8=... (kg)

science (physics)
acceleration due to gravity g= 9.8 m/s^2

Physics
q=2.1μC=2.1•10⁻⁶ C, the side of square ia “a” . The potential at the empty corner due to two charges φ=φ₁+φ₂ = kq/a + kq/a= 2kq/a The potential at the empty corner due to three charges φ`=φ₁+φ̀...

Physics
mg=17.1 N => mg= kx k=mg/x On the moon mg`=kx₁ x₁=mg`/k =m•1.6•g•x /mg=1.6x=1.6•0.044=0.0704 m

Physics
q=2.1μC=2.1•10⁻⁶ C, the side of square ia “a” . The potential at the empty corner due to two charges φ=φ₁+φ₂ = kq/a + kq/a= 2kq/a The potential at the empty corner due to three charges φ`=φ₁+φ̀...

Physics
I=const R=R1+R2+R3 +....=

science
Use Newton's 3 law: You can get back to your station if you throw your reaction jet away

Physics
R1=R(AD)+R(DC)=4+4= 8Ω R2=R(AB)+R(BC)= 4+4= 8Ω 1/R =1/R1 +1/R2= 1/8 + 1/8= 2/8= 1/4 R= 4 Ω

physics
Average speed =distance/time= (150+150)/120 =2.5 m/s Average velocity= displacement/time= 0

Physics
I=U/(R1+R2) =2.4/(12+8) =1.2 A, U1= I•R1= 1.2•8 = 9.6 V, U2= I •R2=1.2•12=14.4 V.

Physics
W=ΔKE= mv²/2 =0.02•150²/2=…

Physics
http://www.citycollegiate.com/wave_soundXc.htm

Physics
this is the inertial motion

physics
T(K) =t℃ +273

Physics
d sinθ = 4λ

Physics -- please help
y=gt²/2 =9.8•0.19²/2 =4.9•0.19² = … For finding the distance you need v(x) s=v(x)• t

Physics
The period is T= 2π•sqrt(m/k) = =2•3.14•sqrt(0.22/12) =0.85 s. It doesn’t depend on „x“

science
mv²/2 =mgh h= v²/2g

physics
I believe that m= 5.1 X 10^- 3 kg F(electr) + F(spr) = mg, qE + k•ΔL=mg E=( mg- k•ΔL)/q= ={5.1•10⁻³•9.8 – 2.4(0.074-0.059)}/6.6 =… V/m

Physics
L(dB) = 10 log₁₀(P₁/P₀)= 10 log₁₀100000= =10•5=50

Physics
T=30/50 = 0.6 s. v=s/t= 0.5/15 = 0.033 m/s λ=vT=0.033•0.6= 0.02 m

physics Electricity
(a) F=k•q₁•q₂/r²=.... k =9•10⁹ N•m²/C² attraction (b) the law of conservation of charge: q(total) = -20+50 = 30 μC The charge on each sphere is q=15 μC F =k•q²/r² = … repulsion

Physics
T₁ =27+273=300 K p₁V₁/T₁= p₂V₂/T₂ T₂ = T₁•p₂V₂/p₁V₁= …. K (!)

Physics
v(n) = ℏn/m•r = e²/4•π•ε₀•ℏ•n= =v₁/n=2.19•10⁶/n m/s n=1 v₁=2.19•10⁶ m/s

physics
mv²/2=k•q₁q₂/r r = 2k•q₁q₂/mv², where k =9•10⁹ N•m²/C² e =1.6•10⁻¹⁹ C. q₁=2e, q₂=79e m=6.64•10⁻²⁷ kg v=2.6•10⁶ m/s

Physics
p1V1 =p2V2 V2=p1V1/p2 d. 0.25 m^3

Physics
v(x0) =v(x)=8 m/s v(y0) =0 v(y)=gt=10•3.8=38 m/s v=sqrt{v(x)² +v(y)²} = =sqrt (8²+38²) = 38.8 m/s

Physics
F(net) = F-F(res) =(2.06-1.75)•10³=0.31•10³=310 N a=F(net)/m= 310/1300=0.24 m/s² s=at²/2=… v=at = …

Physics
W=q•Δφ q= W/Δφ=4.5•10⁻⁴/(300-150)= 3•10⁻⁶C Since this motion takes energy q= - 3•10⁻⁶C

physical
v=ωR=2.08•0.25 =… (m/s)

physical
v=ωR=2.08•0.25 =… (m/s)

Science
http://www.currentresults.com/Weather-Extremes/US/hottest-cities-winter.php

Physics
m₁g=kx k= m₁g/x ω=sqrt(k/m₂)=… (rad/s) f=ω/2π=…(Hz)

Physics
speed is the magnitude of velocity speed ===scalar velocity === vector

physical sciences
when the angle between them is zero

science
STP =standard temperature and pressure: T= 273.15 K p=10⁵Pa μ for hydrogen =2 g/mol= 0.002 kg/mol R=8.31 J/mol•K. m=1g=0.001 kg From pV=mRT/μ V= mRT/μp

Physics
93 km/h=93000/3600=25.8 m/s Centripetal acceleration is a=v²/R=25.8²/1350 =0.49 m/s² The average acceleration = =Δv/Δt = (v₂-v₁)/Δt Since velocity is vector, vecor Δv can be found as vector difference (taking into account that vel...

Physics
F =G•m₁•m₂/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², Solve for R

Physics
F =G•m₁•m₂/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², m₁ =10.7 kg Sove for m₂

Physics
Earth’s mass is M = 5.97•10²⁴kg, G =6.67•10⁻¹¹ N•m²/kg², R=5 • 6.378•10⁶ = .. (a) mv²/R = G•m •M/R² v=sqrt{ G •M/R) = … (b) T=s/v =3πR/v

Physics
mg = G•m •M/R² where R = 6.378•10⁶ m, 100%=12.89% =87.11%. mg₁ =0.8711mg => G•m •M/(R+h)² = 0.8711 G•m •M/R² 0.8711(R+h)² = R² 0.8711 (R² +2Rh+h²) = R² Solve for h

Physics
kq₁/x²=kq₂/(6-x)² 2/x²=6/(6-x)² 36-12x+x²=3x² 2x²+12x-36=0 x²+6x-18=0 x = - 3±sqrt(9+18) = = - 3 ± 5.2 If q₁ >0 and q₂>0 x= 2.2 cm (to the right from the left charge (between the charges)) If q...

Science
PE->KE mgh=mv²/2 v=sqrt(2gh)

physics
C=q/U q= CU

physics
A=4πr² => r=A/4π φ=kq/r k =9•10⁹ N•m²/C² φ=516 V, A= 1.01 m^2 q= φr/k=φA/4πk=..

Physics
A•B= |A||B| cosα cosα =A•B/ |A||B|= =16/5•5=0.64 α=cos⁻¹α=50.2°

physics please please please help me!
neutral atom q=0; if you remove 2 electrons: q= +2•1.6•10⁻¹⁹= +3.2•10⁻¹⁹ C if you add to electrons: q= - 2•1.6•10⁻¹⁹= - 3.2•10⁻¹⁹ C

PHYSICS PLEASE HELP!
q₁ = q₂ = 2•e⁻ =- 3.2 •10⁻¹⁹ C k =9•10⁹ N•m²/C² F=k•q₁•q₂/r² = ... repulsive

Physics
1/R = 1/2.5 +1/3.5 +1/4 = =0.4+0.2857 +0.25 =0.9357 R=1/0.9357 =1.069 Ohm

Physics
1.3 atm =131722.5 Pa p=F/A=4F/πd². d=sqrt(4F/πp)=...

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