Tuesday
December 6, 2016

# Posts by elena

Total # Posts: 4,386

Dynamics
KE=PE+W(fr) m•v²/2 = m•g•h +F•s= =m•g•s•sinα +F•s. F=m(v²/2s - g•sinα)
July 22, 2013

BTech, Mechanical
For the 1st ball, the time of the upward motion v=v₀-gt v=0 0=v₀-gt t= v₀/g =18/9.8=1.83 s. The height of the 1st ball h= v₀t-gt²/2=18•1.83 - 9.8•(1.83)²/2= =16.53 m The time of the 1st ball downward motion before the 2nd ball begins...
July 22, 2013

Physics
Ice m₁=200 g = 0.2 kg c₁ = 2060 J/kg•K λ =335000 J/kg Water c₂=4183 J/kg•K m₂=? m₁c₁[0-(-5)] + m₁λ+ m₁c₂(21-0) = m₂c₂(65-21) m₂=m₁(5c₁+λ+21c₂)/44 c₂ = =0.2(...
July 22, 2013

dynamics
F=P/v=mgsinα v=P/mgsinα=200/80•9.8•0.06 = 4.25 m/s
July 22, 2013

dynamics
0,06P=Fv=mgv v=0.06P/mg
July 22, 2013

Physics
m=F/a Weight =mg
July 22, 2013

physics
Steel ρ₁ =7800 kg/m³ V₁=m₁/ρ₁=2.6/7800 = 3.3•10⁻⁴ m³ Gasoline ρ₂ = 750 kg/m³ m₂=ρ₂V₂=750•15•10⁻³ =11.25 kg ρ(ave) =( m₁+m₂)/(V₁+V&#...
July 22, 2013

physics
V =m /ρ =41/750 = 0.055 m³ =14.53 gallons V=L•W•D= > D=V/L•W = 0.055/0.4•0.9 =0.15 m
July 22, 2013

physics
a=F/m F1=F/4.5 => a1=a/4.5=12.5/4.5=2.78 m/s^2
July 21, 2013

earth
Solar eClipse http://en.wikipedia.org/wiki/Solar_eclipse Lunar eClipse https://en.wikipedia.org/wiki/Lunar_eclipse
July 21, 2013

Physics
Q= mc Δt mc(50-20) = Mc(90-50) m=M•40/30 = 800•40/30 = 1067 kg
July 21, 2013

physics
cM[t(ini) –t(fin)] = mr cMΔt = mr Δt= mr/cM= 2.5•10⁻³•2260•10³/4183•0.28 = 4.8℃ T(fin) = 90-4.8 = 85.2℃
July 21, 2013

physics
(a) m=ρ•V= ρ•L•W•H=917•160000•45000•250=1.65•10¹⁵ kg (b) Q=mL=1.65•10¹⁵•334000=5.51•10²º J (c) Q/Q(US) =5.51•10²º/8•10¹⁹=6.89 (d) Q/q= 5.51•10&#...
July 21, 2013

physics
At 37.0ºC the heat of vaporization Lv for water is 2430 kJ/kg or 580 kcal/kg. Heat of Fusion and vaporization at 0℃ for water(ice) L(f)= 334 kJ/kg. m(cond) •L(v)=ML(f) M= m(cond) •L(v)/ L(f)= =7.4•10⁻³•2430000/334000 =5.38•10&#...
July 21, 2013

physics
For human body c=3470 J/kg. At 37.0ºC the heat of vaporization Lv for water is 2430 kJ/kg or 580 kcal/kg m•c•Δt= m(cond) •L(v) m(cond) = m•c•Δt/L(v) = =60•3470•0.75/2430000 =6.43•10⁻² kg=64.3 g
July 21, 2013

physics
(a) Stefan-Boltzmann Law R=σT⁴ R=P/A =P/4πR² σT⁴=P/4πR² T =forthroot{ P/4σπR²} = =forthroot{3.8•10²⁶/4•5.67•10⁻⁸•π•(7•10⁸)²} =5744 K (b) P₀= P/4...
July 21, 2013

physics
F(x) = F•cosα
July 21, 2013

physics
(a) ω=sqrt(k/m) = sqrt(305/0.26) = 34.2 rad/s y=Asin ωt = > y=0.28sin34.2t (meters) (b) y=A (longest) A= Asin ωt sin ωt = 1 ωt= π t= π/ω=3.14/34.2= 0.092 s. T=2π/ ω = 2•3.14/34.2 = 0.183 s The shortest spring after T/2...
July 20, 2013

Physics
(a) Stefan-Boltzmann Law R=σT⁴ R=P/A =P/4πR² σT⁴=P/4πR² T =forthroot{ P/4σπR²} = =forthroot{3.8•10² /4•5.67•10⁻⁸•π•(7•10⁸)²} =5744 K (b) P₀= P/4πR...
July 20, 2013

general physics
ρ= m/V= 6.3•10²⁸/1.6•10³=3.93 •10²⁵ kg/m³ m= ρV₁=3.93 •10²⁵•2 •10⁻⁷=7.875•10¹⁸ kg=17.4•10¹⁸ lb
July 20, 2013

general physics
p = 2 atm = 202650 Pa p₀ = mg/a•b = 160/0.4•0.24 =1667 Pa N = p/p₀ =202650/1667=121.6 ≈122
July 20, 2013

general physics
July 20, 2013

general physics
July 20, 2013

physics
(a) m=ρ•V= ρ•L•W•H=917•160000•45000•250=1.65•10¹⁵ kg (b) Q=mL=1.65•10¹⁵•334000=5.51•10²º J (c) Q/Q(US) =5.51•10²º/8•10¹⁹=6.89 (d) Q/q= 5.51•10&#...
July 20, 2013

Physics
Q=Mc ΔT =mL(v) m/M = c ΔT/L9v) = =4183•1.6/2430000 = 0.00275 or 0.275%
July 20, 2013

physics
1.25 kcal = 5233.5 J c(merc) = 139 J/kg•K c(steel) = 470 J/kg•K c(concrete) = 880 J/kg•K c(water) = 4183 J/kg•K ΔT=Q/mc =5233.5/1.25• 139 =30.1º => 50,1º ΔT=Q/mc =5233.5/1.25•470 =8.91º => 28,91º ΔT=Q/mc =...
July 19, 2013

Physics
PE₁=k•q₁•q₂/r₁ r₁=∞ =>PE₁ =0 PE₂=k•q₁•q₂/r₂ r₂= 7.07•10⁻¹² m ΔPE= PE₂ - PE₁=PE₂= = 9•10⁹•8e(-8e)/ 7.07•10⁻¹...
July 18, 2013

Physical Science
A. increasing its thickness R=ρL/A A↑=>R↓
July 17, 2013

physics
The image size of a distant object is simply its angular size multiplied by the lens focal length. 1/f = 1/f₁+ 1/f₂−d/f₁•f₂. f₁= 20 cm =0.2 m f₂= - 8 cm = - 0.08 m 1/f = 1/0.2 – 1/0.08 - 1/0.2•0.08= =5-12.5-62.5 = - 70 f...
July 17, 2013

physics
The image size of a distant object is simply its angular size multiplied by the lens focal length. 1/f = 1/f₁+ 1/f₂−d/f₁•f₂. f₁= 20 cm =0.2 m f₂= - 8 cm = - 0.08 m 1/f = 1/0.2 – 1/0.08 - 1/0.2•0.08= =5-12.5-62.5 = - 70 f...
July 17, 2013

Physics
v =v₀-at t=( v₀-v)/a = s= v₀t - at²/2 =…
July 16, 2013

Physics
Or it may be 60 s after the first 10 s v₃ = v₀+a(t₁+t₂) = 10+0.6•(10+60)=52 m/s
July 16, 2013

Physics
v₁=v₀+at₁ a= (v₁-v₀)/t₁ = (16-10)/10 = 0.6 m/s² v₂=v₀+at₂ = 10+0.6•60 = 46 m/s
July 16, 2013

velocity
http://hyperphysics.phy-astr.gsu.edu/hbase/vel2.html http://en.wikipedia.org/wiki/Velocity
July 15, 2013

physics
W=KE=mv²/2
July 15, 2013

Elementary mechanics
the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², M=1.9•10²⁷ kg !!!!!!!!!!!! R=7.15•10⁷ m !!!!!!!! v=sqrt(2GM/R)= =59539 m/s ≈59.5 km/s
July 15, 2013

physics
No. The plane mirror will give an image of the object that is on the opposite side. It creates an erect, virtual image of the same size as the object where the distance from the object to the mirror equals the distance from the image to the mirror.
July 15, 2013

Physics
V=A•L A=V/L R=ρL/A = ρL²/V L=sqrt{RV/ρ} = =sqrt{ 0.15•2•10⁻⁶/1.72•10⁻⁸} = 4.17 m
July 15, 2013

Physics Help
Using Problem 5 page 234 from http://books.google.com.ua/books?id=PQRo3XuHHvYC&pg=PA262&lpg=PA262&dq#v=onepage&q&f=false From steam table at 22.5 bar Hw= 936.48 kJ/kg He = 1865.2 kJ/kg - enthalpy of evaporation (Latent heat) Enthalpy of 1 kg of wet steam is H=Hw+ζ •...
July 14, 2013

Physics Help
Another table http://www.chem.mtu.edu/~tbco/cm3230/steamtables.pdf gives more precise values Hs =2801.7 kJ/kg Hw = 936.48 kJ/kg As a result ζ= (Ht-Hw)/ (Hs-Hw)= =(2279.434-936.48)/(2801.7-936.48) = =13.42.954/1865.22=0.7199 => ≈72%
July 14, 2013

Physics Help
(A)Ht=Hs•ζ+(1-ζ)Hw, where Ht = total (actual) enthalpy (kJ/kg), Hs = enthalpy of steam (kJ/kg), Hw = enthalpy of saturated water or condensate (kJ/kg) Using steam-pressure table http://enpub.fulton.asu.edu/ece340/pdf/steam_tables.PDF we can find the magnitudes ...
July 14, 2013

Physics
p=F/A= mg/πr²= =0.001/3.14•0.0002²=7958 Pa
July 14, 2013

Physics
ρ= m/V =0.240/89•10⁻⁶=2696 kg/m³
July 14, 2013

Physics
PE=KE=KE(transl) + KE(rot) I= mR² mgh = mv²/2 + I ω²/2= = mv²/2 + mR²v²/2R²= = mv²/2+ mv²/2 = mv² v=sqrt(gh)= …
July 14, 2013

Physics
(a) L=Iω= I•2πn=0.4•2π•6 = 15.08 J•s (b) L₁=L₂ I₁•2 πn₁ =I₂•2 πn₂ I₂=I₁•n₁/n₂= 0.4•6/1.25 = 1.92 kg•m² (c) 2 πn₂= 2 πn₁...
July 14, 2013

Physics
PE=KE=KE(transl) + KE(rot). mgh = mv²/2 + I ω²/2= = mv²/2 + I v²/2R². I= (2R²/v²)(mgh- mv²/2)= =mR²(2gh/v² -1) = = mR²(2•9.8•2/36 -1)= =mR²(1.09-1)=0.09 mR²
July 14, 2013

Physics
τ=FR= 180•0.28 = 50.4 N•m I=mR²/2 = 75•0.28²/2=2.94 N•m² τ=Iε => ε= τ/I = 50.4/2.94 = 17.14 rad/s² τ₁=FR-F(fr)r =180•0.28 - 20•0.015 = 50.4 – 0.3 = 50.1 N•m ε₁= τ...
July 14, 2013

Physics
v=500000/3600 =138.9 m/s ω=v/R=138.9/30=4.63 rad/s n= ω/2π=4.63/2 π=0.74 rev/s
July 14, 2013

Physics
F₁+mg=F₂ ….(1) 2•F₁+1•mg=1.5•F₂…(2) From (1) F₁ =F₂ -mg ….(3) Substitute (3) in (2) 2(F₂ -mg) +mg = 1.5•F₂ F₂=2mg=.... F₁=mg= ....
July 14, 2013

physics
KE=mv²/2
July 14, 2013

PHYSIC
KE=PE+W(fr) KE=mv²/2 PE= mgh W(fr) =F(fr) •s=µmgcosα•h/sinα mv²/2 =mgh+µmgcosα•h/sinα Solve for ‘v’
July 14, 2013

physics
s=s₀+vt= =0.2-0.5•20 = - 9.8 m
July 14, 2013

Physics
F=Δp/Δt=mΔv/Δt= =m[v₂-(-v₁)]/Δt= =m(v₂+v₁)/Δt= =1.2•(6+2)/ Δt=… Check the given data (time of contact!!!!)and substitute it
July 13, 2013

physic
W = F • d = Fx•rx + Fy•ry = (12 N) (13 m) + (−1 0 N)(+11 m) = 156 -110=46 J
July 13, 2013

physic
mv²/R=GmM/R ² v= sqrt (GM/R) =… T=2πR/v= …
July 13, 2013

College Physics
ω₁= √(g/L₁) ω₂=√(g/L₂) 1.8 ω₁=ω₂ 1.8√(g/L₁)=√(g/L₂) 1.8²g/L₁=g/L₂ L₂=L₁/3.24=10/3.24 = =3.086 ≈3.19 m = 309 cm
July 13, 2013

College Physics
v= 7 moles, T₁=300 K V₁=1000cm³= 10⁻³ m³ V₂=0.316•10⁻³ m³ W= {(vRT₁)/(γ-1)} •[1-(V₁/V₂)^(γ-1)]= γ=(i+2)/I =(3+2)/3 = 5/3 γ-1=5/3 -1 =2/3= 0.667 W=- {(vRT₁)/(γ-1...
July 13, 2013

phy
F₁=G•m•M/R₁² F₂ =G•m•M/R₂² F₁/F₂=R₂²/R₁² F₂=F₁•R₁²/R₂²= …
July 13, 2013

physic
F₁=G•m•M/R₁² F₂ =G•m•M/R₂² F₁/F₂=R₂²/R₁² F₂=F₁•R₁²/R₂²= …
July 13, 2013

The charge of He ion = e The aceleration of ion in the electric field ma=eE a=eE/m KE=mv²/2= m(at)²/2= = (eEt)²/2m ℇ=KE ℇ = hc/λ hc/λ=(eEt)²/2m t={sqrt(2mhc/λ)}/eE= ={sqrt(2•6.65•10⁻²⁷•6.63•10...
July 13, 2013

physic
mv²/R=GmM/R ² v= sqrt (GM/R) v₁/v₂= sqrt(R₂/R₁) =sqrt(1/4.5)=0.47
July 13, 2013

physic
See answer to a similar question below under related questions
July 13, 2013

Physics
0 = m₁v-m₂u u= m₁v/m₂=175•2.75/2400= ...
July 12, 2013

Physics
F=Δp/Δt=mΔv/Δt= =0.063•45/0.03=94.5 N
July 12, 2013

physics
KE=PE=mgh
July 11, 2013

Physics
PE=KE mgh=mv²/2 v=sqrt(2gh)
July 11, 2013

Physics
PE=KE mgh=mv²/2 v=sqrt(2gh)
July 11, 2013

physics
m₁v-m₂u=0 u= m₁v/m₂= =1150•26.7/2030=15.13 m/s
July 11, 2013

gen physics
(a) KE₁ =m₁v²/2 =85.6•4.58²/2=897.8 =898 J. I also can’t obtain the suggested answer (b) and, as a result, the answer (c) (b) According to the law of conservation of linear momentum m₁v =(m₁+m₂)u u= m₁v/(m₁+m₂...
July 11, 2013

Physics
KE(ini) =mv₁²/2 =8•4²/2=…
July 11, 2013

Physics
KE(ini) =mv₁2 =8•4²/2=… KE(fin)= mv₂²/2 =8•12²/2=…. W= KE(fin)- KE(ini)= …
July 11, 2013

Physics
(a) N=q/e=3.2•10⁹/1.6•10⁻¹⁹= 2•10²⁸ (b) The mass of one lead atom is m₀=207.2 amu =207.2•1.67•10⁻²⁷=3.46•10⁻²⁵kg The number of atoms in 8 g of lead N₀=m/m₀=0.008...
July 10, 2013

physics
F=k•q₁•q₂/r² k =9•10⁹ N•m²/C² q₂ =F•r²/k •q₁
July 10, 2013

physics
KE=PE mv²/ 2 =kx²/2 k=m(v/x) ²
July 10, 2013

physics
Pt =E =mv²/2 v=sqrt(2Pt/m) = =sqrt{2•2000•60/1400)= =13.09 m/s
July 10, 2013

Physics
m₁v=(m₁+m₂)u u= m₁v/(m₁+m₂)= =17000•23/(17000+5100)=17.7 m/s
July 10, 2013

physics
ma=Fcosα-F(fr) ma=0 F(fr) = μmg Fcosα= μmg μ=Fcosα/mg = =20•cos30/5•9.8=0.35
July 10, 2013

physics
mv²/R =μmg v=sqrt(μgR) = =sqrt(0.45•9.8•0.12)=0.73 m/s T=2πR/v = 2π•0.12/0.73 = 1.03 s.
July 10, 2013

science
4πR²3/(4πR³) = 3/R = 3/3960=0.00076
July 10, 2013

physics
m₁g+m₂g =(m₁+m₂)g =380+175=555 (m₁+m₂) =555/g=56.6 kg m₁a =T m₂a=-T+m₂g m₂a = - m₁a +m₂g a=(m₂g)/(m₁+m₂) = =175/56.6=3.1 m/s²
July 10, 2013

physics[
(a) a=5.0 m/s² (b) a depends on power of the engine which doesn’t depend on the mass of fuel
July 9, 2013

physics
ma=mg-F(res) F(res) = m(g-a) = 78(9.8-7.4) = 187.2 N
July 9, 2013

physics
F=m₁ a₁ => m₁ =F/a₁ . If m₂=m₁/2 a₂=F/m₂=F/(m₁/2) =2F/m₁ = 2a₁
July 9, 2013

Physics
s₁ = 100 ya=91.44 m v=s₁/t₁ t₂=s₂/v= s₂•t₁/s₁= =100•9/91.44 =9.84 s
July 9, 2013

Physics
λ=v/f => f = v/ λ, v = sqrt(TL/m ), λ=2L, f = sqrt(TL/m )/ 2L= =sqrt(573•0.803/0.363•10⁻³)/2•0.803= =701 Hz
July 9, 2013

Physics
b. A Foccault pendulum (a large mass hanging from a tall structure using on a long wire) T=const during the long period of time
July 9, 2013

Physics
All explanations on the base of formula for period os spring pendulum T=2πsqrt(m/k) (a) m↓=>T↓ i. Shorter (b) iii. Unchanged (c) k↑↓ => T ii. Longer (d) iii. Unchanged
July 9, 2013

Physics
m₁=3.21 kg m₂=15.3 kg m₂g=T m₁v²/R=T m₁v²/R= m₂g v=sqrt{ m₂gR/ m₁}= =sqrt{15.3•9.8•0.855/3.21} = 1.8 m/s
July 9, 2013

physics
ax²+bx+c=0, 14x²-19 x +61 =0, x= [19±sqrt{19²+4•14•61}]/2•14 = =(19±61.5)/28. x₁=2.88 m, x₂=-1.52 m
July 9, 2013

physics
ma=mv²/2s =600•120²/2•400 =10800 P=W/t=[F+F(fr)]s/t = {10800+1200}•400/7.3 = 6.58•10⁵W =894 hp
July 9, 2013

Physics
E=E₁+E₂=k|q₁|/(d/2)²+ k|q₂|/(d/2)²= k/(d/2)²{ |q₁|+ q₂}= =9•10⁹(7.34+4.49) •10⁻⁶/0.1575= =6.76•10⁵V/m (directed to the negative charge)
July 9, 2013

physics
http://engineering.myindialist.com/2009/difference-between-a-heat-engine-refrigerator-and-heat-pump/#.UdxFaztM9u0
July 9, 2013

physics
KE₂-KE₁=W(fr) mv₂²/2 -mv₁²/2 = F(fr)d cosα = =μ•m•g•d•cos180º v₂²/2 - v₁²/2 =μ•g•d• (-1) v₂²/2= v₁²/2- μ•g•d v₂= sqrt(v&#...
July 8, 2013

physics
the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², Earth’s mass is M₁ = 5.97•10²⁴kg, Earth’s radius is R₁ = 6.38•10⁶ m. Moon’s mass is M₂= 7.35•10² kg Moon’s radius ...
July 8, 2013

physics
the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², Earth’s mass is M = 5.97•10²⁴kg, Earth’s radius is R = 6.378•10⁶ m. E(g) = F/m = G•m •M/m(R+h)²= = G•M/(R+h)²= =6.67•10&#...
July 8, 2013

Phyics