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April 19, 2014

Posts by Elena


Total # Posts: 4,310

physics
Imagine that F₂ is along the x-axis, F is along y-axis, and F₁ is directed to the “north-west”. The angle between F and F₁ is α. sin α = F₂/ F₁=1/2 α=30° Thus, the angle between F₁ and F₂ is 90°+30°...

Physics
W=mg

physics
1/λ₁ =Z²R[(1/n²) – (1/m²)] =2²•1.1•10⁷[(1/1²) –(1/3²)] λ₁=2.56•10⁻⁸ m 1/λ₂ =Z²R[(1/n²) – (1/m²)] =2²•1.1•10⁷[(1/2²) –(1/...

physics
E=5eV=8•10⁻¹⁹ J λ=h/p = h/sqrt(2mE) = =6.63•10⁻³⁴/sqrt(2•9.1•10⁻³¹•8•10⁻¹⁹)=5.5•10⁻¹⁰ m

physics
S=Energy per unit time/Area = Nhf/A= =4Nhc/πD²λ= =4•1.42•10¹⁸•6.63•10⁻³⁴•3•10⁸/π•(1.82•10⁻³)²•524•10⁻⁹= =2.07•10⁵ W/m² Electric f...

physics
(a) 1/do+1/di =1/F 1/di=1/F-1/do=1/48.5•10⁻³- 1/3.85•10⁸. di≃48.5•10⁻³m x/di=D/do x=D•di/do =3.48•10⁶•48.5•10⁻³/3.85•10⁸.= =4.38•10⁻⁴ m (b) 1/do₁+1/di₁...

physics
tan(α/2) =x/L => x=L tan(α/2) Coordinate of the second dark fringe is x=(2k+1)Lλ/d L tan(α/2)= (2k+1)Lλ/d d/λ =(2k+1)/tan(α/2)= (2•2+1)/tan3.6°=79.5

Physics
(i) h=gt²/2 t=sqrt(2h/g)=sqrt(2•10000/9.8)=45.2 s. (ii) v=800000/3600 = 222.2 m/s s=vt =222.2•45.2 =10044 m (iii) x=0 (since the horizontal speed of the cargo is constant)

Physics
The speed of sound at 20°C v=343 m/s s=vt=343•3=1029 m

Physics
If the detector (radar)is at rest and the source (moving car that reflects the sound)) is moving away from the detector, the observed frequency f is less than the actual frequency f₀. The speed of sound v =343 m/s f=f₀v/(v+V) V=v(f₀-f)/f =343•(1.5-1.4)&#...

physics
KE=mv²/2 v²= 2•KE/m a= v²/2s F=ma=mv²/2s= 2m•KE/2s m= = KE/s=10/0.005 =2000 N

physics
v₁ =910 m/s m₂=1000 kg v₂=10000 m/s u= 1000 m/s m₁=? (m₁+m₂)u = m₁v₁ +m₂v₂ m₁=m₂(v₂-u)/(u-v₁)= =1000(10000-1000)/(1000-910) = 100000 kg

Trigonometry
find sin2x, cos2x, and tan2x if sinx= -2/sqrt 5 and x terminates in quadrant III

physics
v=v₀+at = 10.5+(4.4•4.2) = 28.98 m/s

Phyics
1. x: ma=mg•sin α –F(fr) y: 0=-mg•cos α +N ma=0 0= mg•sin α-μN= = mg•sin α-μ•mg•cos α tan α = μ =0.4 α=arctan0.4 =21° 2. ma=mg•sin α – μ₁mg•cos α a=g...

Physics
The blocks move with the same acceleration ‘a’ F(fr)= μN m₁g=W₁ => m₁=W₁/g= 77/9.8=7.86 kg m₂g=W₂ => m₂=W₂/g= 114/9.8=11.63 kg x: m₁a=m₁g•sin α -μ₁N₁-T y: 0=-m₁g&...

physics
1. PE=KE PE=mgh=mg•s•sinα KE=mv²/2 mg•s•sinα=mv²/2 v=sqrt(2g•s•sinα) = =sqrt(2•9.8•1.8•sin22°)=3.64 m/s v=at => a=v/t s=at²/2= vt²/2t=vt/2 t=2s/v=2•1.8/3.64 =0.99 s 2. t₁=2t=0.99&...

Science
p=mv=20•5 =100 kg•m/s

Physical Science
(60 W•24hours •30 days)/1000=43.2 kW•h 43.2•0.1$=4.32$

Physics
T=ma=mv²/L m=TL/v²

Physics
An angular speed ω=v₁/R₁=v₂/R₂ v₁/v₂= R₁/R₂=9.8/6.6 =1.48

Physics
T=ma=mv²/R=1.9•2.8²/2.3= 6.48 N

Physics
B= μ₀•I/2π•d= μ₀•q•t/2π•d q=2π•d•B/ μ₀•t= =2π•28•7.3•10⁻⁵/4π•10⁻⁷•2.2•10⁻³=4.64•10⁶ C

Physics
P=Fv F=P/v = 2614/32.1 =81.43 N

Physics
L is the length of the solenoid N is the number of turns d is the diameter of the wire r is the radius of the solenoid (of the turn) Resistance R=ρx/A=4ρx/πd² ρ=1.6•10⁻⁸ Ω•m μ₀=4π•10⁻⁷ H/m U =...

MATH
explain how to construct a perpendicular bisector

Science
the process in which body cells are duplicated in order to grow and repair body tissues is called

Physics
p=mv

physics
W=mg

physics
mg =ma =mv²/R v=sqrt(gR)=sqrt(9.8•0.6)=2.4 m/s

Physics
Work W=F•s•cosθ cosθ= W/F•s= 43/60•2=0.358 θ=69° ma=Fcos θ a=v²/2s= 2.7²/2•2 = 1.82 m/s² m= Fcos θ/a=60•0.358/1.82 =11.8 kg

Physics
Q=mλ=6.68•335000=2.24•10⁶ J

Art
3. wrong woozworldfan!!! 3. c collaborate!!

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=...

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

Physics
T=1/f=1/2= 0.5 s

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

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

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

Physics Classical Mechanics Help ASAP
http://cnx.org/content/m14614/latest/

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

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

physics
W/A =Y(ΔL/L) ΔL=W•L/A•Y= =mg•L/πr²•Y

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

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

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

physics
240N

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

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

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

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

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...

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

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

Physics
P=Fv=mav a=P/mv=4300/900•13.8=0.35 m/s²

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

Physics
P=Fv=mav a=P/mv=4300/900•13.8=0.35 m/s²

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

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

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

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 =…

physics
No

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...

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

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&#...

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

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

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

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• 10̿...

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

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

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

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)

Physics
ApWeight = mg±mv²/R

Physics
mv²/R=mg v=sqrt(gR)

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

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

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...

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

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...

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 =1...

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

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) - mgsi...

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

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= =6.6...

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...

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...

physics
a=v²/s=51²/75 =34.68 m/s²

PHYSICS
ma=F-μ mg a=F/m -μg

physics
a=μ(k)g s=v²/2a

physical
2) power

physics
↧W=m(g-a) ↥W=m(g+a)

magnetis
a. collapse (shorten)

magnets
Work=0

PHYSICS URGENT HELP
PE=qV V-potential

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

electricity and magnets
http://courses.washington.edu/phys431/hall_effect/hall_effect.pdf

PHYSICS
THETA =90

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 pla...

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 flu...

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