Wednesday
April 16, 2014

Posts by elena


Total # Posts: 4,303

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

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 flu...

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

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/...

physics-important fast
a=v²/2s F=ma= mv²/2s

physics
v=ωR t=s/v= s/ ωR=8600/9.1•0.45=2100 s=35 min

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

physics
m₁v=(m₁+m₂)u u= m₁v/(m₁+m₂)= =1.3•4.28/(1.3+0.93)=

physics
m=F/a

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

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

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- m₁v̀...

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

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

physics
elastic

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

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

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

Science HELP!!!!
3. radio waves

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

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

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

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

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 I...

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%

Physics
F₁/A₁=F₂/A₂ F₁=F₂A₁/A₂=mg A₁/A₂= =3100 •9.8•3.7/210 = 535.3 N p=F₁/A₁=535.3/3.7•10⁻⁴=1.447•10⁶ Pa

Physics
ΔL =L αΔT =2 •10⁻²•14•10⁻⁶•70=1.96•10⁻⁵m=1.96•10⁻² mm

Physics
p = ρgh = 1000•9.8•0.61= 5978 N/m²

PHYSICS
X(L)=2πfL X(C) =1/2πfC Z=sqrt{R²+ [X(L)-X(C)]²} ΔVmax = I₀•Z cosφ=R/Z

Physics
y=0.105 m is the correct answer

physics
Describe the configuration of the bent wire

Physics
R=mv/eB m =9.1•10 ⁻³¹kg e =1.6•10⁻¹⁹ C.

magnetism and electricity
Desribe the configuration of the bent wire

physics
μ₀I₁/2πy= μ₀I₂/2π(0.28-y) I₁(0.28-y)= I₂y 30(0.28-y)=50y 80y=8.4 y=8.4/80=0.105 m

physics
r=d/2 =0.5 mm =0.0005 m I(max) = B(cr) c r /2 = 0.01•3•10⁸•0.0005 /2 = 750 A

Physics
a=(F-F(fr))/(m1+m2)

magnetism
r=d/2 =0.5 mm =0.0005 m I(max) = B(cr) c r /2 = 0.01•3•10⁸•0.0005 /2 = 750 A

magnetic field
μ₀I₁/2πy= μ₀I₂/2π(0.28-y) I₁(0.28-y)= I₂y 30(0.28-y)=50y 80y=8.4 y=8.4/80=0.105 m

physics
E=Pt/η=4500•20/0.9=100000 J =0.1 MJ

physics
μ₀I₁/2πy= μ₀I₂/2π(0.28-y) I₁(0.28-y)= I₂y 30(0.28-y)=50y 80y=8.4 y=8.4/80=0.105 m

physics-magnets
b=a•cos45 =0.1 •0.707 = 0.0707 m B=2 (μ₀/4π)(I/b)∫cosφdφ {limits: (- π/4) (+π/2)} =2(μ₀/4π)(I/b)(1+0.707)= =2.1414 •(μ₀/4π) •2/0.0707=6.06•10⁻⁶T

Physics -Solinoid
d)

physics
circle: L=2πR R=L/2π B₀=μ₀I/2R= μ₀I2 π /2L= =μ₀πI/L square: L=4a=> a=L/4 The distance from the center of the square to the midpoint of the side of the square is b=a/2tan45=a/2 B⋄=4B₁=4B= =4(μ₀...

magnetism
μ₀I₁/2πy= μ₀I₂/2π(0.28-y) I₁(0.28-y)= I₂y 30(0.28-y)=50y 80y=8.4 y=8.4/80=0.105 m

Math
a. t > w

Math
B. w > t

math
sin φ=h/L h=Lsin 30=L/2

physics
KE=mv²/2 “v” is the speed of the ball in the frame of reference “connected with” the airplane

physics
ΔE=hf f= ΔE/h=0.33•1.6•10⁻¹⁹/6.63•10⁻³⁴ = =7.96•10¹³ Hz

physics
E=hf=6.63•10⁻³⁴•1.7•10¹³=1.13•10⁻²⁰ J= = (1.13•10⁻²⁰/1.6•10⁻¹⁹) eV = 0.07 eV E=(n+0.5)hf n=(E/hf) - 0.5 = =(1.6•10⁻¹⁹/6.63•10⁻³S...

physics
(a)y(max) = 2k Lλ/2d = k Lλ/d tan φ= k Lλ/L d = k λ/d tan φ₁=1•λ/d tanφ₂=2•λ/d tan φ₂=2•tan φ₁ 2•tan10 φ₂ ≃20⁰ (b) y(min) = (2k+1) Lλ/2d tan φ = ...

Physics
m₀=1.6749•10⁻²⁷kg E=949 MeV=1.52•10⁻¹⁰ J E=mc² = m=E/c² =1.52•10⁻¹⁰/(3•10⁸)²=1.6889•10⁻²⁷kg m=m₀/√(1- β²) (1- β²)=(m₀/m...

currerent amd magnetism
I(max) = B•c•r/2 = =0.01•3•10⁸•0.0005/2 = 750 A

PHYSICS
U₀=U√2 =210•1.41 = 297 V ω=2πf =2π•90=180π rad/s U=U₀ cos ωt= 297 cos 180πt

Physics
a₁=0.8 m/s² v₁=20 m/s a₂=1.2 m/s² v₂=12 m/s bike: the time to rich v₂ is t₂ =v₂/a₂ = 12/1.2 = 10 s. the distance to the meeting point -for bike s= a₂t₂²/2 +v₂(t-t₂) -for bus s=a₁t²...

Physical Science
d/ 2 A1 + 3 CuSO4 = 3 Cu + A12 (SO4)3

physics
http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/assignments/sol8.pdf

Phisics
x=2.2•10⁻² m v=0.65 m/s m=2 kg k =240 N/m => ω=sqrt(k/m) = sqrt(240/2) =11 rad/s x=Asin ωt v= ω Acos ωt tan ωt = xω /v=2.2•10⁻²•11/0.65 =0.372 ωt =20.4° sin ωt=0.349 x=Asin ωt A=x/sin `...

physics
a=F/m v=v(ini)-at km/h -> m/s !!!!

physics
The height of pivot point above the plane of rotation is h cosi=h/Li cosf=h/Lf Lf=Li•cosi/cosf

Physics Important please
L=0.2 m => R=0.1 m mv²/R=qvB q/m= v/RB = 2.39•10⁵/0.1•0.1 = =2.39•10⁷ C/kg helium ion He+ q/m= 1.6•10⁻¹⁹/(4•1.67•10⁻²⁷+9.1•10⁻³¹) =2.39•10⁷ C/kg

physics
x=Asin ωt v=Aωcos ωt a= Aω²sin ωt F=ma=mAω²sin ωt. F(max)=F(fr) F(max)= mA ω² F(fr) =μmg mAω²=μmg μ=A ω²/g=A(2πf)²/g = =5.2•10⁻²(2π•1.86) ²/9.8=0.23

physics
k=mg/x=3.6•9.8/0.018 =1960 f=2.9 Hz => ω=2πf=2π•2.9 = 18.22 rad/s ω²=k/M => M=k/ ω²=1960/(18.22)² = 5.9 kg Δm=M-m=5.9 – 3.6 – 2.3 kg

physics
T=t/N =2.9/6 = 0.48 s T=2π•sqrt(m/k) = > k=4 π²m/T²= …

Physics please HELP
L=0.2 m => R=0.1 m mv²/R=qvB q/m= v/RB = 2.39•10⁵/0.1•0.1 =2.39•10⁷ C/kg helium ion He+ q/m= 1.6•10⁻¹⁹/(4•1.67•10⁻²⁷+9.1•10⁻³¹) =2.39•10⁷ C/kg

Physics
http://ocw.mit.edu/courses/physics/8-01t-physics-i-fall-2004/exams/exam03_pract_sol.pdf

Physics
(a) F=F(dr) P=Fv=500•23 =11500 N (b) F=F(dr)+mgsinα=500+710•9.8•sin2=500+242.8 =742.8 N P=Fv=742.8•23=17085 N

Magnets
mv²/2=qΔφ v=sqrt(2qΔφ/m) = =sqrt(2•2•1.6•10⁻¹⁹•1000/4•1.67•10⁻²⁷) = 3.1•10⁵ m/s mv²/R = qvB R=mv/qB = 4•1.67•10⁻²⁷•3.1•10⁵/2•...

electricity
p=IA= Iπr² τ=pBsinφ (sinφ=1) => τ=pB

Physics
http://www.csupomona.edu/~skboddeker/131/131hw/ch6h.htm

Physics
http://people.physics.tamu.edu/kattawar/solutions%20218h%20exam2%20f11.PDF

physics
p=F/A =mg/4A₀ A₀=mg/4F

science
N=N₀exp(-ln2•t/T) ln{N/N₀) = -ln2•t/T t= - ln{N/N₀)•T/ln2= = - ln(3.25/26) •713•10⁶/ln2 = = 2.14•10⁹ years

electromagnets
ΔPE=Work W=∫τ•dφ=∫pBsinφ•dφ= =∫IABsinφ•dφ=∫Iπr²Bsinφ•dφ= =Iπr²Bcosφ (limits of integral are π/2 and 0)= Iπr²B W=Iπr²B=2•π•0...

electricity and magnetism
p=IA= Iπr² τ=pBsinφ (sinφ=1) => τ=pB

science
http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/mirray.html

physics
v=sqrt{v(p)²+v(w)²-2v(p)v(w)cos α}= =sqrt{100²+30²-2•100•30cos45} =81.6 km/h s= vt=81.6•3=244.8 km β= 85° (northeast)

physics
v=sqrt{v(p)²+v(w)²-2v(p)v(w)cos α}= =sqrt{100²+30²-2•100•30cos45} =81.6 km/h s= vt=81.6•3=244.8 km β= 85°v (northeast)

Physics
1/λ=R(Z-1)²(1/n² - 1/m²) R=1.1•10⁷ m⁻¹ Z=29 n=1 m=∞ 1/λ=R(Z-1)²=1.1•10⁷•28². λ=3.25•10⁻⁹ m.

Warren (physics)
Q=Q₁+Q₂+Q₃ = c₁mΔT₁+ λm + c₂mΔT₂= = m(c₁ΔT₁ + λ+c₂ΔT)= =0.0132(2060•11.9+ 335000+4183•30)= =0.0132(24514+335000+125490)= =6402 J

Science
B. Vertically through the center of Earth and through each pole.

physics
F(x) =Fcosα F(y)=F sinα

Physics
ΔQ=ΔU+W ΔU= ΔQ-W=2438-897 =1541 J ΔU=νcΔT=ν(iR/2) ΔT ΔT=2 ΔU/νiR =2•1541/3•3•8.31=41.2 K ΔT= T₂-T₁ T₂=T₁+ΔT=396+41.2=437.2 K

Physics
a. g=9.8 m/s² b. Upward: v=v₀-gt v=0 => t=v₀/g =8/9.8 =0.82 s. t(up) =t(down) t(total)=2•0.82=1.64 s. c. v=v₀=8 m/s

physics
T=2πsqrt(R³/GM)

Physics
mv²/2 =MV²/2 V=v•sqrt(m/M) = =350sqrt(50•10⁻³/80)= =8.75 m/s mv²/2=mgh h= v²/2g=350²/2•9.8 =6250 m

Physics
a=v²/2s F=ma

Physics
mv²/2=qΔφ v=sqrt(2qΔφ/m) = =sqrt(2•2•1.6•10⁻¹⁹•1000/4•1.67•10⁻²⁷) = 3.1•10⁵ m/s mv²/R = qvB R=mv/qB = 4•1.67•10⁻²⁷•3.1•10⁵/2•...

physics
I=P/4πR² = 35.5/4π•917² = 3.36•10⁻⁶W/m² I₀= 10⁻¹² W/m² Sound level (in dB) β=(10dB)log(I/I₀) = =10•log(3.36•10⁻⁶/10⁻¹²) =65.2 dB

electromagnets
F=qvBsinα= =1.6•10⁻¹⁹•4•10⁶•0.5•sin60= =2.77•10⁻¹³ N a=F/m=2.77•10⁻¹³/1.67•10⁻²⁷=1.66•10¹⁴ m/s²

physics
I=P/4πR² = 35.5/4π•917² = 3.36•10⁻⁶W/m², I₀= 10⁻¹² W/m², Sound level (in dB) β=(10dB)log(I/I₀) = =10•log(3.36•10⁻⁶/10⁻¹²) =65.2 dB

Physics
q=k•A•ΔT/Δx=0.8•4•10•(50-30)/0.15 =4267 W Q=qt=4267•12•3600=7.86•10¹¹ J

physics
Young’s Modulus E=17•10⁹ N/m² σ=Eε mg/A=E(ΔL/L) ΔL= mgL/AE= 4mgL/ πD²E= =4•12900•9.8•9.4/π•0.42²•17•10⁹= =5•10⁻⁴ m=0.5 mm.

physics
http://answers.yahoo.com/question/index?qid=20100103015632AABnYzd

physics
http://answers.yahoo.com/question/index?qid=20121115115746AAMELdR

Physics
m₁a=- m₁g+T₁ …….(1) - m₂a=T₂- m₂g ……(2) Iε=(T₂-T₁)R => T₂-T₁ = Iε/R=Ia/R² If the wheel is disc I=mR²/2 => T₂-T₁= Iε/R= mR²a/2R²=ma/2 subtract (2...

Physics, Chemistry, Science
• The majority of gas used in most SCUBA tanks is compressed air. This air is composed of the same elements everywhere - 21% Oxygen 79% Nitrogen. Advanced SCUBA divers may use an "enhanced" mixture of 32% (up to about 40%) Oxygen with the balance being Nitrogen....

Physics
s=at²/2 a=2s/t²=2•0.939/0.6²=5.22 m/s² F=ma=2.2•5.22=11.484 N

Physics
s=at²/2 a=2s/t²=2•0.939/0.6²=5.22 m/s² F=ma=2.2•5.22=11.484 N

physics
http://answers.yahoo.com/question/index?qid=20090617182342AAVRQWx

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