# Posts by Elena

Total # Posts: 4,389

**Physics**

v₀⒳=v₀•cosα v₀⒴=v₀•sinα L=vₒ²•sin2α/g,

*June 25, 2013*

**Please help how do I calculate this**

Hot water lost Δ H₁=CmΔT₁ =4.180• 25•(51.5-35) =1724 J Cold water got Δ H₂=CmΔT₂ =4.180• 25•( 35-25) =1045 J Δ H = Δ H₁-Δ H₂=1724-1045=679 J heat capacity of the calorimeter (Calorimeter...

*June 25, 2013*

**Physics**

F=ma=mv²/2s

*June 25, 2013*

**Physics**

F=ma=mv/t

*June 25, 2013*

**physics**

pV=mRT/M => ρ =m/V = pM/RT => RT=pM/ ρþ U= miRT/2M = =mipM/2M ρ =mip/2 ρ= =1•5•80000/2•4 = 50000 J

*June 25, 2013*

**Physics (Stress & Strain)**

σ= F/A A=1•2.5=2.5 cm²=2.5•10⁻⁴m² σ= 150000/2.5•10⁻⁴=6•10⁸ N/m². Strain is defined as "deformation of a solid due to stress" and can be expressed as ε= σ/E, where E= Young’s ...

*June 24, 2013*

**Physic (Stress & Strain)**

L=1.9 m, A= 11 cm²= 11•10⁻⁴m² F=5450 N ΔL = 2.42 mm =2.42•10⁻³ m Stress σ= F/A = 5450/11•10⁻⁴=4.95•10⁶ N/m²= =4.95 MPa Strain ε = ΔL/L= 2.42•10⁻³/1.9 =1.27•10&#...

*June 24, 2013*

**physics**

PE=mgh

*June 24, 2013*

**physics**

http://gmanacheril.com/PHY2048/Text%20Materials/Lesson%204.4%20Conditions%20of%20Equilibrium.pdf Example #2

*June 24, 2013*

**Physics**

P₁₀₀>P₂₅ => U²/R₁₀₀ > U²/R₂₅. Since U = const => R₂₅>R₁₀₀

*June 24, 2013*

**Physics**

50/km/h=13.9 m/s m•a=N•sinα 0=N•cosα - m•g m•v²/R=N•sinα = m•g•sin α/cos α =m•g•tan α tan α = v²/gR =13.9²/9.8•59.9=0.329 α = tan⁻¹=18.19⁰

*June 24, 2013*

**physics**

a=(F-R)/m = (4500-1500)/2000=1.5 m/s^2

*June 24, 2013*

**physics**

Mv₁=mu+Mv₂ u = M(v₁-v₂)/m = = 208(27.9-20.1)/45.9 = =35.3 m/s

*June 24, 2013*

**Physics**

Work =power x time

*June 23, 2013*

**physics**

v(vert) = sqrt (2gh) = =sqrt(2•9.8•0.8)=3.96 m/s

*June 23, 2013*

**physics**

d=sqrt{(8-6)²+5²}= 5.4 m

*June 23, 2013*

**physics**

n=R/A A=R/n = 0.6/1.31=0.458 m http://www.saburchill.com/physics/chapters3/0004.html

*June 23, 2013*

**Physics**

E=F/q=0.032/0.003=10.67 V/m, E= - grad φ E=Δφ/Δx= Δφ/d => Δφ=Ed= 10.67•0.04=0.427 V. ΔPE = - Work of electric field= =-q•Δφ=-0.003•0.427= -1.28•10⁻³ J. Δφ=V. C=εε₀...

*June 20, 2013*

**Physics**

F=eE=1.6•10⁻¹⁹•2805 = 4.5•10⁻¹⁶ N

*June 20, 2013*

**Physics**

ℰ=Δφ=1378 V mv²/2=qΔφ v=sqrt(2qΔφ/m)=…

*June 20, 2013*

**Physics**

the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², F₁₂ =G•m₁•m₂/y²= ... F₃₂ =G•m₃•m₂/x²= ... F=sqrt(F₃₂²+F₁₂²)=... φ is the ...

*June 20, 2013*

**physics**

Average speed = =Total distance/ total time = = 2s/{t₁ +t₂} = = 2s/{s/v₁) +(s/v₂)} = =2v₁v₂/(v₁+v₂) = =2•30•45/(30+45) = 36 km/h

*June 20, 2013*

**Physics (Intro)**

f=ω/2π =sqrt(k/m)/ 2π f=N/t=20/5=4 Hz

*June 19, 2013*

**physics**

C=εε₀A/d ε=1 ε₀=8.85 •10⁻¹² F/m A=1•1=1 cm²=1•10⁻⁴ m² C=q/U=q/Ed ε₀A/d= q/Ed q=ε₀AE=8.85 •10⁻¹²•1•10⁻⁴•1•10⁶= =...

*June 19, 2013*

**science**

c) Pascal/s law

*June 19, 2013*

**science**

a) Uranium

*June 19, 2013*

**science**

d) Gold

*June 19, 2013*

**science**

mv=(m+M)u u=mv/(m+M) = 4•10/(4+40) = 0.9 m/s d) 1 m/s

*June 19, 2013*

**science**

a) AgNO3

*June 19, 2013*

**science**

T=0⁰C = 273 K, p= 1.01325•10⁵ Pa, M=(12+16+16) •10³ = 40•10³ kg/mol. V=mRT/Mp= = 0.004•8.31•273/44•10⁻³•1.01325•10⁵= =0.00204 m³= 2.04 L

*June 19, 2013*

**Physics**

W = m•g =G•m•M/R² g= G•M/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², Earth’s mass is M = 5.97•10²⁴kg, Earth’s radius is R = 6.378•10⁶ m.

*June 18, 2013*

**physics**

PE=KE+PE₁ mgH = mv²/2 + mgR v²= 2g(H-R) at point A N=mv²/R =2mg(H-R)/R= =2•4.3 •10⁻³•9.8•(0.8-0.31)/0.31 = = 0.133 N

*June 18, 2013*

**Physics**

Δh= 13•4.47 m ΔPE =mgΔh = 86.9•9.8•13•4.47= =49487.6 J

*June 18, 2013*

**physics**

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

*June 18, 2013*

**physics**

υ = 1.5 mol p= 3 atm = 303975 Pa V=7 L = 0.007 m³ R=8.31 J/mol•K T=? pV= υRT T=pV/υR= =303975•0.007/1.5•8.31=170 K

*June 18, 2013*

**physics**

the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², Earth’s mass is M = 5.97•10²⁴kg, Earth’s radius is R = 6.378•10⁶ m. r = 850000 m ma=F mv²/(R+r)= G•m•M /(R+r)² v=sqrt{G•M /(R+r...

*June 18, 2013*

**physics**

Wavelength = speed/frequency

*June 18, 2013*

**physics**

I=q/t q=Ne t=2πR/v I=Nev/2πR= =10¹¹•1.6•10⁻¹⁹•3•10⁸/2π•300 = =0.0025 A

*June 18, 2013*

**physics**

v=v₀-gt v=0 t=v₀/g=14/10=1.4 s

*June 17, 2013*

**physics**

λ= 630•10⁻⁹ m, d= ? μm = ? •10⁻⁶ m L=4 m k=1 x=? d•sin φ =k•λ sin φ=k•λ/d φ=sin⁻¹(k•λ/d) tan φ= x/L x=L•tan φ

*June 17, 2013*

**Physics**

s=v²/2a

*June 17, 2013*

**physics**

H-h= gt²/2 t=sqrt{2(H-h)/g} = =sqrt{2(51.5-12.9)/9.8}=2.8 s. v=gt =9.8•2.8=27.44 m/s h₁=12.9 – 1.6 =11.3 m h₁=vt₁+gt₁²/2 gt₁² + vt₁-h₁= 0, t₁² + 27.44t₁- 11.3 = 0, t₁² + 2.8t₁...

*June 17, 2013*

**Physics**

Δh=H-h= gt²/2 t=sqrt(2•Δh/g)= =sqrt{2• (3520-1760)/9.8}=18.95 s. s=vt=10•18.95=189.5 m

*June 14, 2013*

**Physics**

t=s/v=2300/320=7.1875 h

*June 14, 2013*

**Physics**

initial position d₀=0, The maximum height at the motion with initial velocity v₀=20 m/s is H=v₀²/2g=20²/2•9.8 = 20.4 m (!!!) H=v₀t-gt²/2, v(fin)= v₀ -gt, v(fin)=0, => 0= v₀ -gt => v₀ =gt, H=gt²-gt²/2...

*June 14, 2013*

**Physics**

Electric field on the axis of the ring at the distance ‘x’ from the center of it is E = k xq/{sqrt(R²+x²)}³ k=1/4πε₀ The test charge is in equilibrium => E₁=E₂ k x₁q₁/{sqrt(R²+x₁²)}³= =k x...

*June 13, 2013*

**physical science**

Buoyant force=Weight ρ•V₁•g = Weight V₁=x•y•z₁ ρ•x•y•z₁•g = Weight z₁=Weight/ ρ•x•y•g = =445/1000•4•3•9.8=0.0038 m =3.8 mm

*June 13, 2013*

**physics**

The second law for rotation M=Iα => α=M/I M₁/I₁=M₀/I₀ => M₁/M₀=I₁/I₀ I₁ = I₀ => M₁ = M₀ F₁x₁=F₀x₀ F₁/F₀=x₀/x₁=x₀/2x₀ =1/2

*June 13, 2013*

**Physics**

The reflectivity R represents the fraction of the incident light that is reflected at the interface R=I/I₀, where I₀ and I are the incident and reflected beams intensities respectively. If the light is normal (or perpendicular) to the interface, then R={(n₂-n...

*June 13, 2013*

**physics**

tangent to the path

*June 12, 2013*

**Physics**

Suppose that the bullet hits the aim at the upward motion, then h= v₀₁•sinα•t - gt²/2 = v₀₂•sinβ•t - gt²/2, v₀₁•sinα = v₀₂•sinβ , sinβ= v₀₁•sin&#...

*June 9, 2013*

**physics**

http://web.mit.edu/8.02t/www/materials/StudyGuide/guide02.pdf page21

*June 8, 2013*

**Physics**

n=2.7 rev/s => ω=2πn=2•3.14•2.7 ≈17 rad/s ma=F(fr) mω²R=μmg μ=ω²R/g =17²•0.026/9.8 =0.77

*June 8, 2013*

**physics**

F=ma F=eE ma = eE a=eE/m= 1.6•10⁻¹⁹•10³/9.1•10⁻³¹= =1.76•10¹⁴ m/s² s=v₀²/2a = v₀²m/2eE= =(5•10⁶)²•9.1•10⁻³¹/2•1.6•10⁻¹...

*June 8, 2013*

**Physics**

under the action of a torque the dipole aspires to be established along the field

*June 8, 2013*

**Physics**

under the action of a torque the dipole aspires to be established along the field

*June 8, 2013*

**Physics**

v₀=110 km/h=30.6 m/s s=v₀t-at²/2, a=2(v₀t-s)/t²=… v= v₀-at=…

*June 7, 2013*

**Honors Physics- Help PLEASE- Test tmrw**

E=Δm•c²= =9.106•10⁻³•1.67•10⁻²⁷•(3•10⁸)²=1.37•10⁻¹²J

*June 4, 2013*

**Physical Science**

1A, 2B, 3B,D 4A, 5D, 6D, 7A, 8 ??? λ=v/f

*June 4, 2013*

**Physical Science**

1C. at a particular instant. 2A. 4 meters 3B. how fast a velocity is changing at a specific instant 4D. all of the above 5A. the amount of time needed to travel the distance. 6D. The train’s acceleration is negative. 7D. by adding the vectors

*June 4, 2013*

**physics**

ω=2π/t, v= ωR, R= v/ω=vt/2π= =24•0.1/2π=0.38 m.

*June 4, 2013*

**PHYSICS**

σ=F/A=F/πr² ε=ΔL/L Hook’s law for the wire: k ε= σ k= σ/ ε= F L /πr²ΔL E=k•ΔL²/2= F• L•ΔL²/2πr²ΔL= =F•L•ΔL/2πr²=49•5•10⁻...

*June 3, 2013*

**Difracction problem**

For CuKα-radiation λ=1.541•10⁻¹⁰ m. From equation sin²θ₁/(h²+k²+l²)₁=sin²θ₂/(h²+k²+l²)₂=…. const, sin²θ₁/1= sin²θ₂/2= sin²θ...

*June 2, 2013*

**Physics 1 College Level**

the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², mg =GmM/R², g =G M/R²= =6.67•10⁻¹¹•77.89•10²³/(7.9•10⁶)²= =8.32 m/s²

*June 1, 2013*

**Physics 1 College Level**

R=sqrt(D²+d²)=sqrt(3204²+1247²)=3438 m The angle between R and D is cos α =D/R =3204/3438 α=21.26⁰ mass of the spaceship m=? mass of asteroid M=? F₁=GmM/R²=… F=2F₁cos α=…

*June 1, 2013*

**physics**

Q=cmΔT=1800•7•(70-35)=441000 J

*June 1, 2013*

**physics**

F•Δt=Δp=m•Δv= m(v-0) v= F•Δt/m = 80•0.04/0.058=55.17 m/s

*June 1, 2013*

**physics**

sinα =F₁/F₂=0.5 α= 30⁰, the angle between the two forces = 90⁰+30⁰=120⁰

*June 1, 2013*

**MIT 2.01x**

http://aerostudents.com/files/materialsAndStructures/Hibbeler8thEditionBookSolutions/Chapter%2005.pdf

*May 31, 2013*

**Phyics help please varify the answer is correct**

If RT ia the total R then Rt increases

*May 31, 2013*

**physics please need help**

tanφ=X(L)/R = 250/125 = 2 φ=tan⁻¹2=63.4⁰

*May 31, 2013*

**Mathematics Ms Sue help**

band-pass filter http://www.ibiblio.org/kuphaldt/electricCircuits/AC/AC_8.html

*May 31, 2013*

**physics please need help**

f=1/T=1/10⁻³=1000 Hz

*May 31, 2013*

**Phyics please help ms sue**

An open resistor is a resistor with one of the leads not connected.An open resistor can have no current or voltage, and it can have no effect on any circuit. => 35 Ω and 55 Ω are shorted and 100 Ω is open => ℰ=IR =100•10⁻³• 90 = ...

*May 31, 2013*

**Phyics please help ms sue**

W = Watt (unit of power) Resistance: Ohm =Ω => total resistamce R=100 Ω+35 Ω+55 Ω=190 Ω According to Ohm's Law ℰ=IR =100•10⁻³•190 =19 V ≠ 9 V.

*May 31, 2013*

**physics**

ma=F mv²/R=qvBsinα circular path = >sinα = 90⁰ q=e= e =1.6•10⁻¹⁹ C, m=9.1•10⁻³¹ kg R=mv/eB = =9.1•10⁻³¹•3•10⁷/1.6•10⁻¹⁹•0.2 = …

*May 31, 2013*

**physics**

Q=0.75V²t/R= =0.75•120²•15•3600/144=4050000 J = 4.05 MJ

*May 30, 2013*

**Physics**

φ=ω₀t-εt²/2 ω =ω₀-εt ω=0 ω₀=v/r φ=2πN ε =ω₀²/2φ =v²/2r²•2πN= = v²/4πr²N=36²/4•π•0.3²•40=28.6 rad/s²

*May 30, 2013*

**physics**

E=mc²

*May 29, 2013*

**physics**

E=mc² m=E/ c²

*May 29, 2013*

**physics**

β= v/c=0.3c/c=0.3 L=L₀•sqrt{1-β²)=30•sqrt(1-0.3²)=28.6 m

*May 29, 2013*

**physics**

t=t₀/sqrt{1-β²)=11/sqrt(1-0.7²) = 15.4 s

*May 29, 2013*

**physics**

P=F/A=NW/A N=PA/W = =1.013•10⁵•0.203•0.089/17.8=102.8 ≈103

*May 28, 2013*

**English**

These are questions from Stephen King's collection "different seasons", particularly the novel "Rita Hayworth and the shawshank redemption": 1. From all the appearances the trial against Andy was pretty much "opens & shut". Identify the ...

*May 28, 2013*

**Physics**

h=v₀t+gt²/2 gt²+2 v₀t-2h=0 10 t²+3.4t-90 =0 t= {- 3.4±sqrt(11.56+3600)}/20= = { - 3.4 ± 60.1}/20 t = 2.83 s

*May 28, 2013*

**physics**

P=W/A= W/4πr², W=4πr²•P= =4•3.14•(6.37•10⁶)²•1.01•10⁵=5.15•10¹⁹ N

*May 28, 2013*

**Physic Please Help**

sqrt =square root, arctan = tan⁻¹ - inverse trigonometric function – (Broken Link Removed)

*May 28, 2013*

**Physic Please Help**

v=sqrt{(pl)²+v(wind)²} = ... α= arctan{ w(pl)/v(wind)}=... north of west

*May 28, 2013*

**Physics ASAP**

http://www.physicstutorials.org/home/mechanics/1d-kinematics/projectile-motion?start=1

*May 28, 2013*

**Physics ASAP**

t =sqrt(2h/g) s =vt

*May 28, 2013*

**physics**

ΔV/V = αΔT, ΔT = ΔV/ α•V= =0.0015V/V•5.1•10⁻⁵= =0.0015 / 5.1•10⁻⁵= 29.4, t=20+29.4 =49.4℃

*May 28, 2013*

**physics**

p= m₁v₁-m₂v₂= 1500•20 - 950•26 = = 30000- 24700 =5300 kg•m/s

*May 28, 2013*

**physics**

0=m₁v₁cosα + m₂v₂. v₁= - m₂v₂/m₁ cosα= = - 1.25•4/0.60•cos30 = - 9.62 m/s

*May 28, 2013*

**Physics Acceleration**

Δp=p₂-(-p₁) = p₂ + p₁ = m(v₂+v₁), F= Δp/Δt=ma , m(v₂+v₁)/Δt = ma, a= (v₂+v₁)/Δt= =(46+38)/1.05•10⁻³=8•10⁴ m/s²

*May 26, 2013*

**physics**

mg´=mω²R₂=m4π²R₂/T², g´=4π²R₂/T², mg´= G•m•M/R₂², mg= G•m•M/R₁², mg´/mg = G•m•M•R₁²/R₂²•G•m•M, g´/g...

*May 26, 2013*

**PHySICS**

x=kLλ/d λ=xd/kL= =4.2•10⁻³•1.15•10⁻³/3.9•2=6.2•10⁻⁷ m red

*May 26, 2013*

**Physics**

F(1x)=F(1)=10 N F(2x)=F(2)cos60=5•0.5=2.5 N F(2y) =F(2)sin60 = 5•0.866= 4.33 N F(3x) =- F(x)=- (10+2.5 )= -12.5 N F(3y) =- F(2y)= - 4.33 N F(3) = sqrt{ F(3x)²+F(3y)²} =13.23 N tan φ = F(3y)/F(3x) =4.33/12.5=0.364 φ = 19.1⁰ (south-west)

*May 25, 2013*

**Physics**

s=BC=1 m a) PE=KE₁ mgh = mv₁²/2 v₁=sqrt(2gh)=… b,c) KE₂=PE(spring) mv₂²/2 =kx²/2 v₂=sqrt{ kx²/m} =… KE₁=W(fr)+KE₂ mv₁²/2 = μmgs+ mv₂²/2 μ=(1/mgs)•{ mv₁²...

*May 25, 2013*

**Physics**

The circumference of the axel is L=πd, the string wraps around the axel N=s/L= s/ πd. The angle of rotation is φ=2πN=2 πs/ πd=2s/d= =2•80/2=80 rad

*May 25, 2013*

**science**

L=vₒ²•sin2α/g= vₒ²•2sinα•cosα/g h= vₒ²•sin²α/2g, h/L = vₒ²•sin²α•g / vₒ²•2sinα•cosα• 2g= =tan α/4=tan45/4=1/4=0.25 h=0.25L=0.25...

*May 22, 2013*