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July 2, 2015

Posts by Elena


Total # Posts: 4,369

Physics
Q=mλ=6.68•335000=2.24•10⁶ J
February 26, 2014

Physics
F =G•m₁•m₂/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², F=6.67•10⁻¹¹•0.005•10/0.25=...
January 22, 2014

Physics
mgsinα=F sinα=F/mg=3.06x10^6/1.39x10^4 =0.022 α= 1,26 degr
January 13, 2014

Physics
T=1/f=1/2= 0.5 s
January 13, 2014

physics
h=gt²/2 t=sqrt(2h/g) x=v(x) •t => v(x) =x/t=x/sqrt(2h/g) = =8.3/sqrt(2•4.3/9.81)=8.9 m/s
January 11, 2014

Physics
v= v₀+at=30.55-0.805•20=14.5 m/s =14.5•3600/100=52.04 km/h
January 11, 2014

Science question
Coal is solid, the other substances are liquids and gas Answ A http://library.thinkquest.org/3646/earth/resources/fosfuels.html
January 10, 2014

Physics Classical Mechanics Help ASAP
http://cnx.org/content/m14614/latest/
January 10, 2014

physics
mgh=mv²/2 v=sqrt{2gh} =sqrt{2•9.8•2.9} =7.5 m/s v(fin)=v-at v(fin)=0 a=v/t x=vt -at²/2=vt/2 mv²/2 =W(fr) = F(fr) •x => F(fr)= mv²/2x = 2mv²/2 vt=mv/t = =70•7.5/0.58 = 905.2 N
January 10, 2014

physics
a) W+Fx =80•0.882=70.56 J b) W=KE =mv²/2 v=sqrt(2W/m) = sqrt(2•70.56/15)=3.07 m/s c) KE=W(fr) =F•x F=W(fr)/x=KE/x=F/x = 70.56/0.045=1568 N
January 9, 2014

physics
W/A =Y(ΔL/L) ΔL=W•L/A•Y= =mg•L/πr²•Y
January 7, 2014

Physics help quick!
The force is directly proportional to 1/r2 where r is the distance. 19 AU 9.8 N/kg
January 7, 2014

science
q=K(ΔT/Δx)WL= =0.84•19•0.9•1.5/0.004 =5386.5 W
January 7, 2014

physics
Weight on one foot =480/2=240 N Pressure under her soles =Weight/area = =240/area of one sole
January 5, 2014

physics
240N
January 5, 2014

physics
PE=W(fr) kx²/2=μmgd d= kx²/2μmg= =124•2.1²/2•0.7•7•9.8 =5.7 m
January 5, 2014

physics
m₁v₁-m₂v₂=-m₁u₁+m₂u₂ u₂= (m₁v₁-m₂v₂+m₁u₁)/m₂= =(1250•30-2000•25+1250•10)/2000 = 0
January 5, 2014

Need help World Geography
1.B 2.D http://en.wikipedia.org/wiki/Slum
January 4, 2014

Physics
A) W=∫F•dx=-∫kx•dx (limits ↓0↑x) =kx²/2 or ΔW=F•Δx =-kx •Δx, W=ΣΔW= Σ(-kx•Δx)= =- kx Σ{(0-x)/2}= kx²/2 B) W= kx²/2=80•0.35/2 =14 J
January 3, 2014

physics
h=gt²/2 => t=sqrt(2h/g) =sqrt(2•73/9.81) =3.86 s v(y) = gt = 9.81•3.86 =37.87 m/s v=sqrt{v(x)²+v(y)²} =sqrt{37.87²+40²}=55.08 m/s p=mv=Pv/g =177•55.08/9.81 =993.85 kg•m/s tan α =v(y)/v(x) =37.87/40 =0.947 α=arctan0.947...
January 3, 2014

AP Calculus AB
y´=3(cosx)²(-sinx) -3(sinx)²cosx= = - 3 sinx cosx(cosx+sinx)
January 3, 2014

Need help World Geograpy
3A 6C 7C 10B 12C 13D 17D 18B 20B
January 3, 2014

Physics
P=Fv=mav a=P/mv=4300/900•13.8=0.35 m/s²
January 2, 2014

physics
PE=KE mg(H+h) =mv²/2 v=sqrt{2g(H+h))
January 2, 2014

Physics
P=Fv=mav a=P/mv=4300/900•13.8=0.35 m/s²
January 2, 2014

Physics
Q =q•W•L•t= 1380•1000•1300•12•3600= =7.75•10¹³ J Q=cmΔT ΔT= Q/cm = Q/cρV=7.75•10¹³/4180•1000•1000•1300•300= =0.048 K
January 2, 2014

Physics
m₁=36 kg, c₁= 880 J/kg•K, m₂=4 kg, c₂=387 J/kg•K Q=m₁c₁ΔT + m₂c₂ΔT = = ΔT(m₁c₁ + m₂c₂). ΔT= Q/(m₁c₁ + m₂c₂)= =60000/(36•880+4•387) = 1.8 K
January 2, 2014

Physics
a=dv/dt= -b+2ct =-0.31+2.1•10⁻³•36= =-0.2344 m/s² P=Fv=ma•v = 1264•0.2344•18.36 = 5439.7 W
January 2, 2014

physics
Y=2•10¹¹ Pa ω=2πf =2π•2=4π rad/s. ma=T-mg m ω²R =T – mg T=m(ω²R+g) =m(16π²R +g)=… T/A =Y•ΔL/L ΔL=TL/AY =…
January 2, 2014

physics
No
January 2, 2014

physics
V=53•10⁶ ft³=1.5•10⁶ m³ h=45720≈46000 m The density of the air ρ=2•10⁻³ kg/m³ The buoyant force is F=mg= ρVg=2•10⁻³•1.5•10⁶•9.8 =29400≈ 30000 N Answer (d) M=800 kg m...
January 1, 2014

Physics
W(horse) =W(fr) =μNs= μmgs m=W/ μ gs= 8000/0.25•9.8•62=52.7 kg If the rope is horizontal and v=const => T= F(fr) = μmg=0.25•52.7•9.8 =129 N
January 1, 2014

Physics 221
E=Δφ/Δx PE->W(work of electric field) -> KE W=e•Δφ=e•E•Δx KE= mv²/2 mv²/2= e•E•Δx v=sqrt{2•e•E•Δx/m}= =sqrt{2•1.6•10⁻¹⁹•1000•0.001/9.1•10&#...
December 31, 2013

Physics
mv²/2 = kx²/2 +μmgs ==== W(spring) = kx²/2=... E(fr) = μmgs=... v =sqrt{kx²/m +2μ gs}=...
December 31, 2013

Physics - please help me..
W(block) =kx²/2=252•0.29²/2=10.6 J W(spring) = - 10.6 J mv²/2 = kx²/2 v=x•sqrt(m/k)= =0.29•sqrt(0.395/252) =0.0115 m/s
December 31, 2013

physics
KE(rot)=Iω²/2 =MR²ω²/2•2 KE(tr)=0.25•KE(rot) KE(tr)=0.25•MR²ω²/4 mv²/2 = MR²ω²/16 v=(Rω/4)•sqrt{2M/m)=4.5 m/s C. 4.5 m/s
December 30, 2013

physics
M= 5.97•10²⁴ kg m=500 kg r = 6.378•10⁶ m. R= 2• 0⁶ km= 2• 10⁹ m GmM/r-GmM/R = mv²/2 GM(1/r -1/R) = v²/2 v=sqrt{2GM(r-R)/rR}= =sqrt {2•6.67•10⁻¹¹• 5.97•10²⁴(2• 10&#...
December 27, 2013

science
During 1 period El→Mag→El→Mag→El => T= 4•2 μs= 8 μs=8•10⁻⁶ s f=1/T=1/8•10⁻⁶=1.25•10⁵ Hz
December 26, 2013

physics
v=sqrt{2•6.67•10⁻¹¹•1.5•1.98•10³º/10⁴}= =1.99•10⁸ m/s ≈2•10⁸ m/s
December 25, 2013

physics
C. M=1.5•1.98•10³º kg G =6.67•10⁻¹¹ N•m²/kg² mv²/2=GmM/R v=sqrt{2GM/R}=2•10⁸ m/s
December 25, 2013

Physics
PE ->KE KE ->PE(spring) => PE= PE(spring) mgh=kx²/2 x=sqrt(2mgh/k)=… PE(spring) -> KE->PE => the same ‘h’ (due to the absence of friction)
December 25, 2013

Physics
ApWeight = mg±mv²/R
December 24, 2013

Physics
mv²/R=mg v=sqrt(gR)
December 24, 2013

Physics
a=g•tanθ T= sqrt{(ma)²+(mg)²}= =m•sqrt{a²+g²}
December 24, 2013

Physics
1. PE(B)=KE+PE(A) mgh= KE+mg2R KE= mgh- mg2R= =mg(h-2R) 2. mgh= mv²/2+mg2R v²= 2g(h-2R) a= v²/R= 2g(h-2R)/R 3. mgh= mv²/2+mg2R h= v²/2g +2R
December 24, 2013

physics
The total energy at the top point is mv²/2+mg2R. It is equal to the energy at lower point. Its height is h=R-Rcosθ = R(1-cosθ) => the total energy is mv₁²/2 +mgR(1-cosθ). Use the law of conservation of energy. mv²/2+mg2R = mv₁²...
December 24, 2013

physics
E=h²n²/8ma² Read http://www.umich.edu/~chem461/QMChap3.pdf
December 23, 2013

physics
V=8000cm³=8•10⁻³m³ p=2 atm= 2.03•10⁵Pa T=273 K ν=pV/RT = 2.03•10⁵•8•10⁻³/273•8.31 = = 0.716 moles V=const p₁/T₁=p/T p₁=T₁p/T=373•2.03•10⁵/273 =2.77•10&#...
December 23, 2013

physics
Δp•Δx≥h Δx=d=10⁻⁵ Δp•d ≥h Δp≥h/d=6.63•10⁻³⁴/10⁻⁵=6.63•10⁻²⁹ b. change in p greater or equal to 10^-29 kg m/s mΔv•Δx≥h Δx=d = m =...
December 23, 2013

physic
a= v²/R=420²/430 =410.2 m/s² F=ma=1750•410.2 =717907 N
December 22, 2013

physics
α=25º, β =35º, m=80 kg, μ=0.7 Fcosβ - F(fr) - mgsin α = 0 N+Fsinβ – mg cos α = 0 N= mg cos α - Fsinβ F(fr) = μN = μ(mg cos α – Fsinβ) Fcosβ -μ(mg cos α – Fsinβ) - ...
December 21, 2013

physics
My mistake in the last line =1.22•10⁻¹¹ m=12.2 pm
December 20, 2013

Physics 11 Forces Unit
1. F =G•m₁•m₂/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², F =G•m₁•m₂/R²= =6.67•10⁻¹¹•(4.15•10⁸)²/60²=3191 N 2. g`=GM/R²= =6....
December 19, 2013

Physics AP
cos φ=0.25/1.2 =0.208 => φ=78° sinφ=0.98, tan φ=4.7. x: ma=Tcosφ y: 0=Tsinφ-mg a=v²/R, Tsinφ=mg Tcosφ= mv²/R Tsinφ/Tcosφ= mgR/ mv² tanφ= gR/v² v=sqrt{gR/tanφ}=sqrt(9.8•0.25/4.7) =0.72 m...
December 19, 2013

physics
KE=10⁴•1.6•10⁻¹⁹ =1.6•10 ⁻¹⁵J KE=mv²/2 =m²v²/2m =p²/2m => p=sqrt(2m•KE) λ=h/p =h/sqrt((2m•KE)= =6.63•10⁻³⁴/sqrt(2•9.1•10 ⁻³¹•1.6&#...
December 19, 2013

physics
a=v²/s=51²/75 =34.68 m/s²
December 18, 2013

PHYSICS
ma=F-μ mg a=F/m -μg
December 18, 2013

physics
a=μ(k)g s=v²/2a
December 18, 2013

physical
2) power
December 18, 2013

physics
↧W=m(g-a) ↥W=m(g+a)
December 18, 2013

magnetis
a. collapse (shorten)
December 18, 2013

magnets
Work=0
December 18, 2013

PHYSICS URGENT HELP
PE=qV V-potential
December 18, 2013

magnets
Prob. 9 http://www-physics.ucsd.edu/students/courses/winter2010/physics2b/hw/hw8.pdf
December 18, 2013

electricity and magnets
http://courses.washington.edu/phys431/hall_effect/hall_effect.pdf
December 17, 2013

PHYSICS
THETA =90
December 17, 2013

physics
The current in the loop and magnetic field direction are connected according to the right hand rule: curl fingers to the direction of the current in the loop, the thumb points in the direction of magnetic moment of the loop that coincides with the direction of B. => The ...
December 17, 2013

magnetism
Let x be the distance from the right end of the rails to the rod. Magnetic field of the long straight wire is B=μ₀I/2πr If the infinitesimal horizontal strip of length x and width dr, parallel to the wire and a distance r from it => area A = x dr and the ...
December 17, 2013

manetism help!
F=qvB mv²/R=qvB R=mv/qB T=2πR/v=2π mv/qBv= =2π m/qB T1=T2 (T doesn’t depend on v)
December 17, 2013

Physical science
When the balls are moving in opposite directions v₁= {-2m₂v₂₀ +(m₁-m₂)v₁₀}/(m₁+m₂) v₂={ 2m₁v₁₀ - (m₂-m₁)v₂₀}/(m₁+m₂)
December 17, 2013

Physics multiple choice
1- b) False 2 -c) 10 N [up] 3 - d) 400 N
December 17, 2013

Physics
Constant v = 2πR/T=2π•7.3/34 = 1.3 m/s Constant centripetal acceleration is a=v²/R =1.3²/7.3 = 0.23 m/s²
December 17, 2013

PHYSICS PLS HELP
a)theta=pi/2
December 17, 2013

Physics
At the top point v=0 => time of upward motion of the 1st stone is t=v/g =22.7/9.8=2.32 s. Δt =2.32 -2.14 =0.18 s. At t=2.32 s the 1st stone is at the top point h₁=v₀t-gt²/2 =27.7•2.32 – 9.8•2.32²/2 =37.9 m with v=0 and begins its ...
December 17, 2013

Physics
PE-> KE -> PE(springs) mgh =23 kx²/2 x=sqrt{2mgh/23k} = =sqrt{2•43•9.8•1.93/23•6000} =0.012 m
December 16, 2013

Physics
F=ma E=F/e=ma/e E=Δφ/Δx => Δφ =E Δx= ma Δx /e= =9.1•10⁻³¹•10¹²•0.04/1.6•10⁻¹⁹=0.2275 V
December 16, 2013

Physics Elena Help pls
Let x be the distance from the right end of the rails to the rod. Magnetic field of the long straight wire is B=μ₀I/2πr If the infinitesimal horizontal strip of length x and width dr, parallel to the wire and a distance r from it => area A = x dr and the ...
December 16, 2013

science plz help right now!!!!
1 B 2 D 3 c 4 d 5 c 6 b 7 d 8 b
December 16, 2013

Physics
Distance between the current I₀ and I is b=sqrt{0.015²+0.1²} =0.101 m. According to Bio-Savart Law, the magnetic fields (B₁=B₂) created by the currents lying on the ground at the point where current I is located are B₁=B₂=μ₀I/...
December 16, 2013

physics-important fast
a=v²/2s F=ma= mv²/2s
December 13, 2013

physics
v=ωR t=s/v= s/ ωR=8600/9.1•0.45=2100 s=35 min
December 13, 2013

Physics-urgent
s=v(t+3) s=at²/2 v(t+3) =at²/2 at²-2vt-6v=0 t²-10t-30=0 t=12.42 s s= v(t+3)=20(12.42+3) = 308.4 m
December 13, 2013

physics
m₁v=(m₁+m₂)u u= m₁v/(m₁+m₂)= =1.3•4.28/(1.3+0.93)=
December 12, 2013

physics
m=F/a
December 12, 2013

Physics
a=(v₂-v₁)/t= [78 – (-23)]/27 =3.74 m/s²
December 12, 2013

PHYSICS HELP!
m₁v₁-m₂v₂=(m₁+m₂)u u =(m₁v₁-m₂v₂)/(m₁+m₂)= … ΔKE=m₁v₁²/2 + m₂v₂²/2 -(m₁+m₂)u²/2=..
December 12, 2013

physics HELP!
m₁=0.004 kg, v₁₀=0.26 m/s m₂=0.012 g, v₂= -0.13 m/s v₁=? m₁v₁₀ = m₁v₁ +m₂v₂ v₁= (m₁-m₂)v₁₀/(m₁+m₂) ΔKE = m₁v₁₀²/2- m₁v&#...
December 12, 2013

physics
F=Δp/Δt =m(v₂-v₁)/Δt v₂ =0 Δt= m v₂/F=(-0.2•25.2)/(- 387)= 0.013 s a= - v₁/Δt=-25.2/0.013 = - 1938.5 m/s² s=- v₁²/2a=-25.2²/2•(-1938.5)=0.16 m
December 12, 2013

physics
Velocity in the stretched string is v = sqrt(TL/m) For the 3rd harmonic λ=2L/3 λ=v/f => v= λf=2Lf/3 sqrt(TL/m)= 2Lf/3 TL/m=(2Lf/3)² m=9TL/4L²f²=9T/4Lf²= =9•100/4•1.8•79²=0.02 kg=20 g
December 12, 2013

physics
elastic
December 12, 2013

physics
h=gt²/2 => t=sqrt(2h/g) L=vt=v• sqrt(2h/g)
December 12, 2013

physics
h=gt²/2 => t=sqrt(2h/g) L=vt=v• sqrt(2h/g)
December 12, 2013

Physics Classical Mechanics
http://web.mit.edu/8.01t/www/materials/InClass/IC_Sol_W09D3-2.pdf
December 12, 2013

Science HELP!!!!
3. radio waves
December 10, 2013

physics
At rest: circle A=πR² Motion with v=0.8c r=Rsqrt(1-β²) =R(1-0.8²) =0.6R Area of the ellipse A₁=πRr=π0.6R² =0.6A
December 8, 2013

Physics Classical Mechanics
http://web.mit.edu/8.01t/www/materials/InClass/IC_Sol_W13D1-8.pdf
December 8, 2013

physics help
http://web.mit.edu/8.01t/www/materials/InClass/IC_Sol_W13D1-8.pdf
December 8, 2013

physics
http://www.columbia.edu/~crg2133/Files/Physics/8_01/lotsOfProbs.pdf Prob/ #29
December 6, 2013

physics
α=12•10⁻⁶ K⁻¹ T₁=22° T₂=-28°, T₃= 48° ΔT₁ = T₃-T₂ = 48-(-25) = 73° ΔT₂ =48-22 = 26° ΔL₁=L αΔT₁=9•12•10⁻⁶•73=0.0079 m ...
December 3, 2013

Physics
for stell α=(11-13) •10⁻⁶ K⁻¹ take α=12•10⁻⁶ K⁻¹ ΔA=A₀2 αΔT ΔA•100%/A₀=2αΔT•100%= =2•12•10⁻⁶ 220•100%= 0.528%
December 3, 2013

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