# Posts by Elena

Total # Posts: 4,389

physics
PE=kx²/2 k=2•PE/ x²= =2•2.5/0.15²=222 N/m

physics
PE =KE =KE(trans)+ KE(rot) = mgL=mv²/2 +Iω²/2= =m ω²L²/2 + m ω²L²/3•2= =2 m ω²L²/3, ω=sqrt(3g/2L)=sqrt(3•9.8/2•1.2) = =sqrt(12.24)=3.5 rad/s

physics
mg= F =G•m •M/(R+h)² g= G•M/(R+h)² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², h=3600000 m=3.6•10⁶ m Earth’s mass is M = 5.97•10²⁴kg, Earth’s radius is R = 6.378•10&#...

Physics
F(fr)=μ•N=μ•m•g•cosα

Physics
F(fr)=μ•N=μ•m•g μ=F(fr)/mg

Science
The most common mineral of the Earth's continents is quartz, the mineral SiO2.

science
http://en.wikipedia.org/wiki/Ion

science
http://en.wikipedia.org/wiki/Isotope

science
http://www.chem4kids.com/files/elem_pertable.html http://en.wikipedia.org/wiki/Periodic_table

science
http://www.chem4kids.com/files/atom_bonds.html

Science
http://www.chem4kids.com/files/atom_electron.html

physics
μ=0.14, s=30 m=160 kg x: m•a= m•g•sinα - F(fr), y: 0= - m•g•cosα +N. F(fr)=μ•N= μ• m•g•cosα m•a= m•g•sinα - μ• m•g•cosα a= g(sinα - μ•cosα...

English
we are learning about the 14 tenses: past,present,future,past perfect,present perfect, future perfect, past progressive..., past perfect progressive..., emphatic..and then there is another one but i forgot what that one was. Anyway, i need a website that can help me with these...

Math
Christine currently has \$5000 in her 401(k) and plans to contribute \$100 each month for the next 30 years into it. What will be the value of Christine's 402(k) in 30 years if the per annum rate of return is assumed to be 12% compounded monthly?

English
We are working on Passive and Active voice. i really don't understand it, so do you know any websites that could help me with passive and active voice.

math
i typed it in my calculator and i got : 1910 but i don't know if that's right? sorry

Math
Christine currently has \$5000 in her 401(k) and plans to contribute \$100 each month for the next 30 years into it. What will be the value of Christine's 402(k) in 30 years if the per annum rate of return is assumed to be 12% compounded monthly?

physics
weight = mg

physics
2.5x/25 = x/do do=25x/2.5x=10cm 1/di+1/do=1/f 1/25 + 1/10 =1/f 7/50=1/f f=50/7=7.14 cm

Physics
N=mgcosα F(fr)= μN = μmgcosα ma=F(fr)+mgsinα => ma= μmgcosα + mgsinα a=g(μcosα+sinα)=.... s=v²/2a=....

Physics
N=mgcosα ma=T-mgsinα => T=m(a+gsinα)

physics please help!
http://www.physics.utoronto.ca/~poptor/solutions05/pss4_optics.pdf

Physics
B.Electric field? A.Magnetic

Physics
index of refraction = c/v=λ(vac)/λ(substance) λ(water) =λ(air)/n=650 nm/1.33=489 nm. This is the wavelength of violet light The swimmer sees the red-orange color since our eyes detect the frequency of the light

Physics
In vacuum v(red)=v(blue)=v(green)= c=3 x10^8 m/s In glass v(red)>v(green)>v(blue)

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

Physics
Yes F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg² (!!!!)

Physics
(a) mv²/2=W(fr) =F(fr)s=μNs=μmgs s= mv²/2μmg= v²/2μg s is the same for the both cars (b) s↑ since μ↓

Physics
(a) using dynamics mgh=mv²/2 v=sqrt(2gh) (b) using kinenatics h=gt²/2 =>sqrt(2h/g) v=gt=gsqrt(2h/g)=sqrt(2gh)

science
L=10 cm, E= 200 GPa=200•10⁹ Pa σ=F/A =350 MPa =350•10⁶ Pa ε= ΔL/L Hook's law E= σ=E•ε=E•ΔL/L, ΔL= σ•L/ E =350•10⁶•10/200•10⁹ =0.0175 cm

Physics
L=0.2 m (a) mg=kx₁ L₁=L+ x₁=L+ (mg/k)=… (b) m•sqrt(g²+a²)=kx₂ L₂=L+x₂= L + m•sqrt(g²+a²)/k = …

physics
The roentgen is the quantity of radiation which liberates by ionisation 1 esu of electricity per 1 cm³ of air under normal conditions of temperature and pressure 1 electrostatic unit of charge (esu) = 3.33•10⁻¹º C 150 mR/hr =150•10⁻³/...

physics
V=60 cm³ 500 mR/min= 500•10⁻³/60 = 8.33•10⁻³ R/s, the charge in 1 cm³ is q= 8.33•10⁻³•3.33•10⁻¹º =2.78•10⁻¹² C in chamber Q=2.78•10⁻¹²•60 =1.67&#...

Physics
The alcohol in the first arm floats on top of the denser glycerin and pressures it down distance h from the initial level. As a result, the glycerin rises by the distance h in the second arm. Due to the equilibrium condition, the point of the two liquids contact in the 1st arm...

Physics
Use T=2π•sqrt(L/g)

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

Science ~conversions~
a= F/m=0.001/1.5•10⁻³=0.67 m/s²

Math 310 Math for Teachers
v(X)=v1 v(Y) = v2 s is the distance between A and B t is the time before the 1st meeting v1•t=120, v2•t=s-120, {(s-120)+(s-90)} =v1•6, v2•6=120+90. => v2=(120+90)/6=210/6=35 mph ----- t=120/v1 (1) 2s-210=6•v1 (2) 35•t=s-120 (3) === Substitute...

physics
m₁v₁²/2 =qU => v₁ =sqrt(2qU/m₁) m₂v₂²/2 =qU => v₂=sqrt(2qU/m₂) v₁/v₂=sqrt(2qU/m₁)/sqrt(2qU/m₂)=sqrt(m₂/m₁) in magnetic field: ma=qvBsinα a=v²/R, α=90°, sin90...

Science
Radioactive decay law N =N₀exp(-λt)= =N₀exp(-ln2•t/T)= =20exp(-0.693•18000/6000) = 2.5 g

Physics
KE=mv²/2 = (mv)²/2m =p²/2m p=sqrt(2m•KE) = ... p=mv => v=p/m=...

Physics
Units????

pHYSICS
water: Q=cmΔT=4180•0.063•(49.7-21.2)=7505.19 J=1792.6 cal peanut: 0.59 g (or kg???) calorie content = 7505.19/0.59•10⁻³ J/kg=1792.6 /0.59•10⁻³ cal/kg =

Physics
Δt=1min/110=60/110=0.55 s FΔt=Δp= mΔv= m[v-(-v)] =2mv F=2mv/Δt =2•0.008•550/0.55 =16 N

Phyiscs
The height of the first stone is h₀=v₀²/2g=27²/2•9.8 = 37.2 m. v=v₀-gt, v=0 => the time of the upward motion is t= v₀/g =27/9.8=2.8 s. The 1st stone was falling down during t₁=5.5-2.8 = 2.7 s, when the 2nd stone started. The 1st ...

physic
v=200 km/h, v₀= 70 km/h, Angle that make v and v₀ is 45° => An angle α in cosine law is α (360°-2•45°)/2 =135° Cosine law: V=sqrt(v²+v₀²-2vv₀cos α)= =sqrt[40000+4900-2•200•70•(-0.707)]=254 ...

Physic
A₁v₁=A₂v₂ (πd₁²/4)v₁=(πd₂²/4)v₂ v₂=(d₁²/d₂²)v₁=(16d₁²/d₁²)1 m/s=16 m/s

Physics
F=ma a=F/m v=sqrt(2as)

Physics
a=F/(m1+m2+m3)

Physics
mgh=mv₀²/2 v₀=sqrt(2gh)=sqrt(2•9.8•10.4)=14.28 m/s v= v₀-at, v=0 => a= v₀/t = 14.28/3.58 =4 m/s² F=ma=68.2•4=272.8 N

Physics- PLEASE HELP
v =331sqrt(T/273) v1=331sqrt(300/273) =347 m/s v2=331sqrt(313/273) =354 m/s Fundamental frequency λ=4L f=v/ λ => f1/f2 =v2/v1 => f2=f1(v2/v1)=715(354/347)=729 Hz f(beat) =f2-f1= 729-715 =14 Hz

physics
v=ω•R=2π•n•R =2π•(1800/60) •0.26=… a(centripetal) = v²/R=…

Physics- Elena please help!
Mass per unit length m(o) =0.011 kg/m T=46 N Speed in the stretched string is v = sqrt(T/m(o)) =sqrt(46/0.011)= 64.7 m/s λ=2L=1.2 m f=v/ λ=64.7/1.2=53.9 Hz Resonant frequency F(n)=n•v/2L=n(64.7/1.2)=53.9•n=20000 n=20000/53.9 =370 => f(n)= n•v/2L=...

Physics
F=F(fr)=μN=μmg

Physics- Someone Please Help!!!
Mass per unit length m(o) =0.011 kg/m T=46 N Speed in the stretched string is v = sqrt(T/m(o)) =sqrt(46/0.011)= 64.7 m/s λ=2L=1.2 m f=v/ λ=64.7/1.2=53.9 Hz Resonant frequency F(n)=n•v/2L=n(64.7/1.2)=53.9•n=20000 n=20000/53.9 =370 => f(n)= n•v/2L=370...

Physics URGENT!!!
f(n) = nv/2L The lowest frequency is f1=v/2L =343/2•0.306=560 Hz. Distance between adjacent antinodes is λ/2 and λ=v/f So λ2=v/2f=343/2•41000 =0.0042 m

Physics
Average speed= total distance /time taken= = 3200/13.5•60 =3.95 m/s Average velocity = total displacement/time taken = 0.

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

Physics
b. emitted electrons are more energetic Einstein's relation for phptoelectric effect: hc/λ=v W= KE, λ↓ KE↑

Physics!!!
y=3.17cos38.6 =3.17 •0.78=2.48 h= 3.17 - 2.48=0.69 v=3.68 m/s

physics
KE=mv²/2 v=sqrt(2KE/m)

Physics HW Help, Please
E= mv²/2

physics
Pascal’s principle F1/A1=F2/A2. F(bc)={A(bc)/A(mc)}•F(pedal) = =(1.83/6.32) •49 =14.2 N This is the normal force exerted on the brake shoe. The frictional force is F(fr) =μ F(bc)=0.442•14.2 =6.3 N

PHYSICS - PLEASE HELP
W=m•g•h=m•g•d•sin30

PHYSICS - PLEASE HELP
W=m•g•h=m•gvdvsin30

Physics
U =mgh-mv²/2

Physics
by 4

PHYSICS - PLEASE HELP
(A) KE₁=m₁v₁²/2= (m₁v₁)²/2 m₁=p₁²/2m₁ KE₂=m₂v₂²/2= (m₂v₂)²/2 m₂= p₂²/2m₂ KE₁=KE₂ p₁²/2m₁=p₂²/2m₂ p₁...

physics
Δy=Lλ/d = 1•500•10⁻⁹/0.001=…

physics
ΔPE=m•g•h=m•g•s•sinα

physics
ΔKE=ΔPE +W(fr)= m•g•s•sinα+μ•m•g•s•cosα= =m•g•s(sinα+μ•cosα)

Physics
v⒳=v₀•cosα v⒴=v₀•sinα L=vₒ²•sin2α/g, h= vₒ²•sin²α/2g, t= 2vₒ•sinα/g

physics
mgh₁=mv₁²/2 mgh₂=mv₂²/2= m(3.9v₁)²/2=15.21 mv₁²/2 h₂=15.21h₁

Physics, Please Help
F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², R=h+R(Earth)= (455+6370)•10³ m

PHYSICS PLEASE HELP ME
The law of conservation of linear momentum vector p₁ +vector p₂ =vectorp₁`+vector p₂` Projections on the axis x and y p₁⒳ +p₂⒳= p₁`⒳+p₂`⒳ p₁⒴ +p₂⒴= p₁`⒴+p₂`⒴...

science
stratovolcano

physics
p₁+ρ‧ν₁²/2 +ρ‧g‧h₁ = p₂+ρ‧ν₂²/2 +ρ‧g‧h₂ p₁ = p₂+ρ(ν₂²-ν₁²)/2 +ρ‧g(h₂-h₁)= =141855 +1354‧...

physics
(a) continuity equation: A₁v₁=A₂v₂ π‧d₁²/4‧v₁=π‧d₂²/4‧v₂ v₂=v₁(d₁/d₂)² =82.4 m/s. (b) p₁=1.4 atm = 141855 Pa h₂-h₁ =-7.82 m Bernoulli ...

Physics
a=F/m

Physics
F=k•q1•q2/r² k =9•10^9 N•m²/C²

math
Write the expression thrice the sum of m and 8

Physics
Units????????

Physics
F(total) =4748 -3969 =779 (directed to the east) Win – Theta Chi It’s better to pull straight on

physics
The pressure at the depth d p1= ρ•g•d + p (atm) =1024•9.8•18.9 + 101325 =2.91•10 ⁵ Pa, The pressure at the height h p=p₀exp{-μgh/RT) Since we don’t know the temperature, we use another expression. Air pressure above sea level...

Physics
sinα=1/20=0.05 sinα=h/s => h=s•sinα W=ΔPE=m•g•h=(m₁+m₂)•g•s•sinα=..

physics
m₁=1500 kg, m₂=2500 kg, v₁=5mph=2.24 m/s, claimed velocity is u=10 mph=4.47 m/s, real speed of the pickup is v₂=? μ=0.49, s=5 m. Law of conservation of linear momentum m₁•v₁+m₂•v₂=(m₁+m₂)•v, law of...

Physics
m=2.5 kg. R=D/2=0.1 m, n₀=3600 rpm=3600/60=60 rev/s t=10 s. F=? 2πn=2πn₀-εt. Final n=0 2πn₀ = εt. ε =2πn₀/t. Newton’s 2 law for rotation: Iε=M. If the wheel is disc I=mR²/2, M=FR. Then (mR²/2) •...

Physics
Tuning fork has frequancy f= 200 Hz +> it makes 200 oscollations during 1 s. Since 1 min=60 s, it makes 200•60=12000 oscillations/min. Each oscillation = 4A=4•0.13 cm=4•0.0013 m=0.0052 m. Therefore, s=0.0052•12000=62.4 m.

physics
Ampere’s force F=ILBsinα F(ℓ)=F/L=IBsinα=7.5•0.7•sin45 = ...

Physics
F(fr)=μN=μmg=0.032 •55.2•9.8=....

physics
Δp=(m1+m2)Δν=(66+7.1)(9.4-6.5)=202 kg•m/s

Physics
t= 2vₒ•sinα/g

physics
h=gt²/2 t=sqrt(2h/g) L=v•t=36•sqrt(2•162/9.8)=… v(x)= 36 m/s v(y)=gt=g•sqrt(2h/g)=...

physics
T=2•π•sqrt(m/k) Solve for ’m’

physics ..PLEASE HELP ASSIGN DUE SOON :(
http://answers.yahoo.com/question/index?qid=20121124093302AA02rcf

physics
T=2π•sqrt(L/g) g=3.7 m/s² Solve for ‘L’

physics
T=2π•sqrt(L/g) g=9.8 m/s² Solve for ‘L’

Physics
Flows to the Earth ΔS(E)=6000/295 =20.34 J/K Flows out of the Sun ΔS(S)=-6000/5650 =- 1.062 J/K ΔS= ΔS(E)+ ΔS(S)= 20.34 -1.062= 19.278 J/K

Physics
Q=r•m ΔS=Q/T₀=r•m/T₀=333•10⁵•0.0951/273=1.16•10⁴ J/K If environment temperature is T, ΔS= - Q/T= - 333•10⁵•0.0951/T= …

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