Wednesday
October 1, 2014

Posts by Elena


Total # Posts: 4,332

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
November 26, 2013

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
November 26, 2013

physics
T=t/N =2.9/6 = 0.48 s T=2π•sqrt(m/k) = > k=4 π²m/T²= …
November 26, 2013

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
November 26, 2013

Physics
http://ocw.mit.edu/courses/physics/8-01t-physics-i-fall-2004/exams/exam03_pract_sol.pdf
November 24, 2013

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
November 23, 2013

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•...
November 23, 2013

electricity
p=IA= Iπr² τ=pBsinφ (sinφ=1) => τ=pB
November 23, 2013

Physics
http://www.csupomona.edu/~skboddeker/131/131hw/ch6h.htm
November 23, 2013

Physics
http://people.physics.tamu.edu/kattawar/solutions%20218h%20exam2%20f11.PDF
November 23, 2013

physics
p=F/A =mg/4A₀ A₀=mg/4F
November 22, 2013

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
November 22, 2013

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...
November 22, 2013

electricity and magnetism
p=IA= Iπr² τ=pBsinφ (sinφ=1) => τ=pB
November 22, 2013

science
http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/mirray.html
November 22, 2013

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)
November 21, 2013

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)
November 21, 2013

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.
November 21, 2013

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
November 20, 2013

Science
B. Vertically through the center of Earth and through each pole.
November 20, 2013

physics
F(x) =Fcosα F(y)=F sinα
November 20, 2013

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
November 20, 2013

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
November 19, 2013

physics
T=2πsqrt(R³/GM)
November 19, 2013

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
November 19, 2013

Physics
a=v²/2s F=ma
November 19, 2013

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•...
November 19, 2013

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
November 19, 2013

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
November 19, 2013

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
November 19, 2013

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
November 19, 2013

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.
November 19, 2013

physics
http://answers.yahoo.com/question/index?qid=20100103015632AABnYzd
November 19, 2013

physics
http://answers.yahoo.com/question/index?qid=20121115115746AAMELdR
November 19, 2013

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...
November 19, 2013

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...
November 18, 2013

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
November 18, 2013

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
November 18, 2013

physics
http://answers.yahoo.com/question/index?qid=20090617182342AAVRQWx
November 18, 2013

Physics
to Anton: F=qvB? where q=e v: m mile/s -> m/s B= 5•10⁻⁵ T
November 18, 2013

Physics
X: m₁v₁=m₁u₁cosα+m₂u₂cosβ Y: 0=m₁u₁sinα - m₂u₂cosβ m₁v₁-m₁u₁cosα = m₂u₂cosβ …(1) m₁u₁sinα= m₂u₂cosβ ……...
November 18, 2013

Science (Physics)
on the Earth W= mg=30•10=300 N on the Moon W₁=mg₁=mg/6 = =W/6 =300/6 = 50 N mg=GmM/R² g=G M/R² => M=gR²/G the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², Earth’s radius is R = 6.378•10⁶ ...
November 18, 2013

Physics
s₁=15 m, a=1 m/s²,t₂=15 s s₁=v²/2a v=sqrt(2as₁) v=at₁ t₁=v/a s₂=vt₂ s= s₁+s₂ t=t₁+t₂
November 18, 2013

Physics- torque
sinα=(3.92-0.506)/8.35 =0.409 α =sin⁻¹0.409 = 24.13º F=832•cosα=832•0.913 =759.6 N τ=759.6•3.92=2977.6 N•m
November 18, 2013

Physical Science
(E) 210/82 Pb -> 210/83 Bi + 0/-1 e + y (C) 49.6 grams
November 18, 2013

physics
sinα=(3.92-0.506)/8.35 =0.409 α =sin⁻¹0.409 = 24.13º F=832•cosα=832•0.913 =759.6 N τ=759.6•3.92=2977.6 N•m
November 18, 2013

physics
h=gt²/2 => t=sqrt{2h/g} => t₁=t₂
November 18, 2013

Physics - pendulum
T₁=2π•sqrt{L/g₁} T₂=2π•sqrt{L/g₂} g₂=g₁(T₁/T₂)²
November 18, 2013

Physics - Oscillations
T=2π•sqrt{m/k} T=t/N t/N=2π•sqrt{m/k} (t/2πN)²=m/k k=m(2πN/t)²
November 18, 2013

physics
F=691+89=780 N p=(F/2)/A=F/2A => A=F/2p=780/2•8.4•10⁵=4.6 10⁻⁴m²
November 18, 2013

physics
ρ=m/V =m/πr²h= =15700/π•1.35²•3.94=696 kg/m³
November 18, 2013

physics
I=mr²/2 mgh= mv²/2 +Iω²/2 = =mv²/2 +mr²v²/r²4 = = mv²/2+ mv²/4 =3mv²/4 v=sqrt{4gh/3} => c)both in same time.
November 18, 2013

Physics
5 N 8.5 N 0 N
November 18, 2013

Physics
- a force that makes the net force on an object zero - It is equal in magnitude and opposite in direction - A moving object in equilibrium continues at a constant velocity.
November 18, 2013

Physics
W = ∫F•dx = a•x + (b/2) •x² - (c/3) •x³ x=0.794 m a = 12600 N, b = 8420 N/m, c = 10100 N/m^2,
November 18, 2013

Physics
when the arrow representing the vector would point toward negative x <-- 10.4 km/h <--
November 18, 2013

Physics, Elena Please Help If u can.
I need the figure
November 18, 2013

physics
Son : m, v Father : M, u M=4m mv²/2=3Mu²/2 => mv²/2=3•4mu²/2 => v²=12 u²…..(1) mv²/2= M(u+1.8)²/2 mv²/2= 4m(u+1.8)²/2 v²= 4(u+1.8)² ….(2) Substitute v² from (1) in (2) 12 u²=4(u+1.8)&#...
November 18, 2013

PHYSICS
m₁a=m₁g-T₁ m₂a=T₂ - m₂gsinα Iε=(T₁-T₂)R => T₁-T₂ = Iε/R=Ia/R²=mR²a/2 R²=ma/2 m₁a+ m₂a= m₁g-T₁+ T₂ - =m₁g- m₂gsinα –( T₁-T&#...
November 18, 2013

physics
T=38.2 N, T₁=28.9 N, T₂=17,4 Buoyant force F In the air T = mg …. (1) In the water T₁=mg-F₁ …..(2) In the unknown liquid T₂=mg-F₂ ….. (3) Substitute (1) in (2) and (3) F₁=mg- T₁=T-T₁=38.2-28.9=9.3 N F₂=...
November 17, 2013

Math- urgent
-3 (x-8)+7x=12 -3x+24 +7x=12 4x=-12 x=-3
November 17, 2013

math
12 persons Each has 2 balloons and 3 prizes
November 17, 2013

physics
Max force the man can apply is F= F(fr)= μN=μmg=0.78•93•9.8=710.9 N Max acceleration a=F/M = 710.9/104000=0.0068 m/s²
November 17, 2013

Math- urgent
If x+4•7=-2 then x+28=-2 x=-30 If x+ 4⁷=-2 then x+16384=-2 x=-16386
November 17, 2013

Math
V=75• 135•0.03=303.75 m³= 303750 L t=V/V₀=303750/250=1215 min=20.25 hours
November 17, 2013

PHYSICS HELP
m₁a=m₁g-T₁ m₂a=T₂- F(fr) 0=m₂g-N Iε=(T₁-T₂)R =>T₁-T₂ = Iε/R=Ia/R² N= m₂g, F(fr)=μN=μm₂g m₁a+ m₂a= m₁g-T₁+ T₂- F(fr)= =m₁g- μm₂g &#...
November 17, 2013

science
a) Mg + 2HCl = MgCl₂ + H₂ b) 2K + 2H₂O = 2KOH + H₂ c) 2Li + 2H₂O = 2LiOH + H₂ d) 4Fe + 3O₂ = 2Fe₂O₃
November 17, 2013

physics
http://www.astro.queensu.ca/~tjb/hw/P10706/hw8_old.pdf
November 17, 2013

Density Problem
density ρ=m/V V=4πR³/3 kilometers -> meters!
November 17, 2013

Science (Physics)
On the Earth h=v²/2g On the Moon H=v²/2g₁ H/h= v²2g/2g₁v²=g/g₁ H=h g/g₁=24.2•9.8/1.6= 148.225 m
November 16, 2013

Phyics
v(max) =Aω= 2πA/T
November 16, 2013

physics
x=Asinωt v=Aωcosωt a=-Aω²sinωt =- ω²x=-(2π/T)²x |a/x| = (2π/T)² T=2 π sqrt{ x/a}=2 π•sqrt(0.235/2.3)=2 s.
November 16, 2013

Physics
Q=cmΔT= 4186•0.6•20 = 50232 J. ΔQ=Q₀-Q=140000-50232=89768 J m₁=ΔQ/λ=89768/335000=0.268 J M=0.6-0.268=0.332 kg
November 16, 2013

physics
http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/raydiag.html
November 16, 2013

Physics
http://mech.subwiki.org/wiki/Limiting_coefficient_of_static_friction
November 16, 2013

Physics
ma=mgsinα-F(fr)=mgsinα-μN= =mgsinα-μmgcosα μ(stat.fr) => a=0 0= mgsinα-μmgcosα μ=tanα
November 16, 2013

Physics
mg=500 N vector T + vecrorT +vector mg = 0 y-projection : 2Tsinα = mg T=mg/2sinα=500/2sin10=1439.7 N
November 16, 2013

Physics
ma=mgsinα-F(fr)=mgsinα-μN= =mgsinα-μmgcosα μ(stat.fr) => a=0 0= mgsinα-μmgcosα μ=tanα
November 16, 2013

Physics
on the Earth W= mg on the Moon W₁=mg₁=mg/6 =9=W/6 =900/6 =150 N
November 16, 2013

Physics
N=mg±Fsinα + if α is measured below the horizontal - if α is measured above the horizontal (a) mgcosα =μN μ = mgcosα/N (b) ma=Fcosα –F(fr) = = Fcosα – μN Solve for ‘a’
November 15, 2013

Physics
W = ∫F•dx = a•x + (b/2) •x² - (c/3) •x³ = =12600•0.794 +8420•0.794²/2 -10100•0.794³/3= =10004.4+2654.1-5055.7 =7602.8 J
November 15, 2013

Physics
W = ∫F•dx = a•x + (b/2) •x² - (c/3) •x³
November 15, 2013

Physics
mgh = mv²/2 v=sqrt(2gh)
November 15, 2013

physics
F(x) =17cos68-19 = F(y) = 17sin68+16.5 = F=sqrt{F(x)²+F(y)²}= tanα =F(y)/F(x)=
November 14, 2013

Physics
F(x)=93.3 +73.1cos45 +181 cos 45 = F(y)=73.1 sin45 -182sin 45 = F=sqrt{F(x)²+F(y)²}=
November 14, 2013

Physics
x: F=Tsinα y: mg=Tcosα F/mg=Tsinα/ Tcosα tanα =F/mg=67.7/14.9•9.8 = 0.46 α =arctan0.46= 24.9⁰ T=F/sinα=67.7/sin24.9=67.7/0.42=161 N
November 14, 2013

physics
a=v²/2s=22²/2•1.55 =156.13 m/s² t=v/a=22/156.13=0.14 s
November 14, 2013

physics
k=F/x=21.3/0.19 = 112 N/m
November 14, 2013

Physics
m₁=6.646•10⁻²⁷ kg, v₁=3.4•10⁶ m/s, m₂=3.287•10⁻²⁵-6.646•10⁻²⁷=3.22054•10⁻²⁵ kg, v₂=? p₁=m₁v₁=6.646•10⁻²⁷•3.4...
November 14, 2013

Physics
v=v₀+at
November 14, 2013

Physics
s=(v₀²-v²)/2a v= sqrt{ v₀²-2as}
November 14, 2013

physics
τ=Iε=(2mR²/5)ε= =2•12•0.22²•12/5 =2.79 N•m
November 14, 2013

Physics Classical Mechanics
http://web.mit.edu/8.01t/www/materials/ProblemSets/Raw/old_files_fall07/ps10sol.pdf
November 14, 2013

Physics Classical Mechanics`
http://ocw.mit.edu/courses/physics/8-01sc-physics-i-classical-mechanics-fall-2010/two-dimensional-rotational-motion/two-dimensional-rotational-dynamics/MIT8_01SC_problems21_soln.pdf
November 14, 2013

physics
R₀=8 Ω, T₀=20℃, R₁=8.4 Ω, T₁=70℃, T₂ = - 10℃ R₂=? R=R₀[1-αΔT] R₁=R₀[1-αΔT₁] 8.4=8[1+(70-20)α] α={8.4/8 – 1)/50 = 10⁻³ K⁻¹ R₂=R...
November 13, 2013

physics Important please
R₀=8 Ω, T₀=20℃, R₁=8.4 Ω, T₁=70℃, T₂ = - 10℃ R₂=? R=R₀[1-αΔT] R₁=R₀[1-αΔT₁] 8.4=8[1+(70-20)α] α={8.4/8 – 1)/50 = 10⁻³ K⁻¹ R₂=R...
November 12, 2013

physics Important please
q=It=Ut/R
November 12, 2013

Phyics
W=mg=ρVg= ρπr²hg= =2.2•10³•π•0.55²•1.9•9.8 = =38929 N=173173 lb
November 12, 2013

phyics
F₁=kx₁ F₂=kx₂ F₁/F₂=x₁/x₂ F₂=F₁x₂/x₁
November 12, 2013

physics
KE=W(resistive force) mv²/2 = Fs F= mv²/2s
November 12, 2013

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