Saturday
February 13, 2016

# Posts by Elena

Total # Posts: 4,375

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...
December 10, 2012

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?
December 10, 2012

English
We are working on Passive and Active voice. i really dont understand it, so do you know any websites that could help me with passive and active voice.
December 10, 2012

math
i typed it in my calculator and i got : 1910 but i dont know if thats right? sorry
December 10, 2012

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?
December 10, 2012

physics
weight = mg
December 10, 2012

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
December 9, 2012

Physics
N=mgcosα F(fr)= μN = μmgcosα ma=F(fr)+mgsinα => ma= μmgcosα + mgsinα a=g(μcosα+sinα)=.... s=v²/2a=....
December 8, 2012

Physics
N=mgcosα ma=T-mgsinα => T=m(a+gsinα)
December 8, 2012

http://www.physics.utoronto.ca/~poptor/solutions05/pss4_optics.pdf
December 8, 2012

Physics
B.Electric field? A.Magnetic
December 8, 2012

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
December 8, 2012

Physics
In vacuum v(red)=v(blue)=v(green)= c=3 x10^8 m/s In glass v(red)>v(green)>v(blue)
December 8, 2012

Physics
F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg²,
December 8, 2012

Physics
Yes F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg² (!!!!)
December 8, 2012

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↓
December 8, 2012

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)
December 8, 2012

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
December 8, 2012

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 = …
December 8, 2012

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/...
December 8, 2012

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&#...
December 8, 2012

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...
December 7, 2012

Physics
Use T=2π•sqrt(L/g)
December 7, 2012

Physics
F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg²,
December 6, 2012

Science ~conversions~
a= F/m=0.001/1.5•10⁻³=0.67 m/s²
December 5, 2012

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...
December 5, 2012

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...
December 5, 2012

Science
Radioactive decay law N =N₀exp(-λt)= =N₀exp(-ln2•t/T)= =20exp(-0.693•18000/6000) = 2.5 g
December 5, 2012

Physics
KE=mv²/2 = (mv)²/2m =p²/2m p=sqrt(2m•KE) = ... p=mv => v=p/m=...
December 5, 2012

Physics
Units????
December 5, 2012

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 =
December 5, 2012

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
December 5, 2012

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 ...
December 5, 2012

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 ...
December 5, 2012

Physic
A₁v₁=A₂v₂ (πd₁²/4)v₁=(πd₂²/4)v₂ v₂=(d₁²/d₂²)v₁=(16d₁²/d₁²)1 m/s=16 m/s
December 5, 2012

Physics
F=ma a=F/m v=sqrt(2as)
December 5, 2012

Physics
a=F/(m1+m2+m3)
December 5, 2012

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
December 5, 2012

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
December 5, 2012

physics
v=ω•R=2π•n•R =2π•(1800/60) •0.26=… a(centripetal) = v²/R=…
December 3, 2012

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=...
December 3, 2012

Physics
F=F(fr)=μN=μmg
December 3, 2012

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...
December 3, 2012

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
December 3, 2012

Physics
Average speed= total distance /time taken= = 3200/13.5•60 =3.95 m/s Average velocity = total displacement/time taken = 0.
December 3, 2012

physics
F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg²,
December 3, 2012

Physics
b. emitted electrons are more energetic Einstein's relation for phptoelectric effect: hc/λ=v W= KE, λ↓ KE↑
December 3, 2012

Physics!!!
y=3.17cos38.6 =3.17 •0.78=2.48 h= 3.17 - 2.48=0.69 v=3.68 m/s
December 2, 2012

physics
KE=mv²/2 v=sqrt(2KE/m)
December 1, 2012

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
November 30, 2012

W=m•g•h=m•g•d•sin30
November 30, 2012

W=m•g•h=m•gvdvsin30
November 30, 2012

Physics
U =mgh-mv²/2
November 30, 2012

(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...
November 30, 2012

physics
Δy=Lλ/d = 1•500•10⁻⁹/0.001=…
November 30, 2012

physics
ΔPE=m•g•h=m•g•s•sinα
November 30, 2012

physics
ΔKE=ΔPE +W(fr)= m•g•s•sinα+μ•m•g•s•cosα= =m•g•s(sinα+μ•cosα)
November 29, 2012

Physics
v⒳=v₀•cosα v⒴=v₀•sinα L=vₒ²•sin2α/g, h= vₒ²•sin²α/2g, t= 2vₒ•sinα/g
November 29, 2012

physics
mgh₁=mv₁²/2 mgh₂=mv₂²/2= m(3.9v₁)²/2=15.21 mv₁²/2 h₂=15.21h₁
November 29, 2012

F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², R=h+R(Earth)= (455+6370)•10³ m
November 29, 2012

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`⒴...
November 29, 2012

science
stratovolcano
November 29, 2012

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‧...
November 29, 2012

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 ...
November 29, 2012

Physics
F=k•q1•q2/r² k =9•10^9 N•m²/C²
November 29, 2012

math
Write the expression thrice the sum of m and 8
November 27, 2012

Physics
Units????????
November 27, 2012

Physics
F(total) =4748 -3969 =779 (directed to the east) Win – Theta Chi It’s better to pull straight on
November 27, 2012

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...
November 27, 2012

Physics
sinα=1/20=0.05 sinα=h/s => h=s•sinα W=ΔPE=m•g•h=(m₁+m₂)•g•s•sinα=..
November 27, 2012

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...
November 26, 2012

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) •...
November 26, 2012

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.
November 26, 2012

physics
Ampere’s force F=ILBsinα F(ℓ)=F/L=IBsinα=7.5•0.7•sin45 = ...
November 26, 2012

Physics
F(fr)=μN=μmg=0.032 •55.2•9.8=....
November 26, 2012

physics
Δp=(m1+m2)Δν=(66+7.1)(9.4-6.5)=202 kg•m/s
November 26, 2012

Physics
t= 2vₒ•sinα/g
November 26, 2012

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)=...
November 26, 2012

physics
T=2•π•sqrt(m/k) Solve for ’m’
November 26, 2012

November 26, 2012

physics
T=2π•sqrt(L/g) g=3.7 m/s² Solve for ‘L’
November 26, 2012

physics
T=2π•sqrt(L/g) g=9.8 m/s² Solve for ‘L’
November 26, 2012

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
November 26, 2012

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= …
November 26, 2012

Physics
m = W•T1/(T1-T2)• r =...
November 26, 2012

Physics
T1=273+170=443 K T2=273+23=296 K efficiency =(Q1-Q2)/Q1 =W/Q1 efficiency =(T1-T2)/T1 W/Q1 = (T1-T2)/T1 Q1=W•T1/(T1-T2) Q1= r•m r= 333•10⁵ J/kg W•T1/(T1-T2) =r•m r= W•T1/(T1-T2)•m=...
November 26, 2012

Physics
W=1,300 J Q2=6,100 J Q1 =? W=Q1-Q2 Q1=W+Q2 efficiency =(Q1-Q2)/Q1 =W/Q1
November 26, 2012

Physics
W= - p•ΔV = -0.8•(-5)•10⁻³•1.013•10⁵ = =405.2 J ΔU =Q+W=-380+405.2=252 J
November 26, 2012

Physics
(a) Ti=273+7.4=280.4 K Vi/Ti = Vf/Tf Vi/280.4 =8 Vi/Tf Tf=8•280.4 = 2243.2 K b) p•ΔV=νRΔT ν =1 mol p•ΔV= RΔT W = p•ΔV= RΔT= = 8.31•(2243.2-280.4)= =1.63•10⁴ J =16.3 kJ
November 26, 2012

physics
When the cart is 14 cm from the left end of the track, it has a displacement of x=14 -11 cm =3 cm= 0.03 m from the equilibrium position. The speed of the cart at this distance from equilibrium is v=sqrt{k(A²-x²)m}=…
November 26, 2012

The Binding Energy of Electrons?
Energy of photon: E = hc/λ h = Planck’s constant = 6.626•10⁻³⁴ J•s = 4.14•10⁻¹⁵ eV•s c = speed of light = 3•10⁸ m/s λ = wavelength = 0.954 nm = 0.954•10⁻⁹m E = 4.14•10⁻...
November 26, 2012

physics
A=4.2 cm = 0.045 m. v(max) =Aω=A•sqrt(k/m)=...
November 26, 2012

physics
T=2•π•sqrt(m/k)= 2•π•sqrt(0.223/10.20)= …
November 26, 2012

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
November 26, 2012