Friday

September 4, 2015
Total # Posts: 4,370

**physics**

If v=const => a=0 f=F(fr)+mg If f is directed vertically N=0 => F(fr)=μN=0 => f=mg
*January 2, 2013*

**mechanics -physics**

averege v =total dostance/total time = =(15•120 + 18•45)/165 =15.82 m/s
*January 2, 2013*

**Physics**

Doppler shift f₀ = f/(1- v/u) = =880/(1-3.5/343)=889.07 Hz
*January 2, 2013*

**Science 8R - HELP!**

http://wiki.answers.com/Q/What_is_the_difference_between_reflection_and_refraction
*January 2, 2013*

**Anyone Please Help!**

Let t be the time of the motion to east => 300•t=400(7-t) 300t=400•7-400t 700t=400•7 t=4 hours s=300•t=300•4=1200 km
*January 2, 2013*

**physical science**

p1=m1•v1 =2000•5=10000 km•m/s p2=m2•v2=0.009•450=4.05 kg•m/s p1> p2 Impulse F•Δt=m•Δv=linear momentum
*January 2, 2013*

**physical science**

t1=t2=sqrt(2h/g)
*January 2, 2013*

**Physics**

h/s=sinα h=s•sinα PE=KE m•g•h = m•v²/2 v=sqrt(2gh) (b) PE=KE+W(fr) m•g•h = m•v²/2 = +F(fr) •s Solve for ‘v”
*December 30, 2012*

**Physics**

At the top point F(centr) =mg
*December 30, 2012*

**Physics**

Torque= force • distance 150 • (0.5-0.2) = 100 • x x= 150•0.3/100=0.45 m (from the center or at the point 0.95 m mark)
*December 30, 2012*

**science**

a=F/m
*December 27, 2012*

**Physics-mechanics**

mv²/R=GmM/R² v=sqrt(GM/R )=sqrt{6.67•10⁻¹¹•6.42•10²³ /(3.40 •10⁶+175 000)}=3.46•10³ m/s. T=2πR/v=2•3.14•(3.40 •10⁶+175 000)/ 3.46•10³ =6.5•10³ s=1.8 h
*December 27, 2012*

**Physics-mechanics**

density ρ =M/V mg=W=GmM/R² => M= WR²/Gm. V=4πR³/3. ρ =3 WR²/4πR³Gm = =3W/4πRGm = =3•9.8/4•3.14•6.4•10⁶•6.67•10⁻¹¹•1= =5.48•10³ kg/m³
*December 27, 2012*

**science**

http://www.visionlearning.com/library/module_viewer.php?mid=37
*December 26, 2012*

**physics**

t= 2vₒ•sinα/g
*December 23, 2012*

**Physics**

(a)If we place one sheet with its polarization direction 90⁰ to the polarized light then the transmitted intensity will be zero (since I=I₀•cos²α = I₀•cos²90⁰=0). If we use 2 sheets, the 1st sheet rotates by angle α (0<...
*December 21, 2012*

**PHISIC help**

KE -> PE(of elastic deformation) -> KE
*December 21, 2012*

**physics**

F=ma=ma=mv²/2s
*December 21, 2012*

**physics**

http://www.chegg.com/homework-help/questions-and-answers/bars-equilibrium-2-m-long-weighing-92-n-string-pullingdown-bars-attached-04-m-fulcrum-left-q1768975
*December 21, 2012*

**Physics**

m1•v1+0 = m1•u(1x) +m2•u(2x) 0=-m1•u(1y) + m2•u(2y) m1•v1 = m1•u1•cos20⁰+m1•u2•cosα 0= - m1•u1•sin20⁰ +m2•u2•sinα . m1•(v1 -u1•cos20⁰)=m1•u2•cosα, .....(1...
*December 20, 2012*

**PHYSICS**

E=5 x 10^5 N/C m =9.1 x 10^-31 kg e= 1.6 x 10^-19 C ma=eE a= eE/m
*December 20, 2012*

**physics**

v1=a1•t1=5.9•4=23.6 m/s v2= a2•t2 = 4.4•6.5 = 28.6 m/s τ1 =s/v1 =200/23.6=8.47 s. τ2 =s/v2 =200/28.6=6.99 s the total time for the 1st runner 4+8.47 = 12.47 s. fir the 2nd runner 6.5+6.99 = 13.49 s
*December 20, 2012*

**PHISIC help**

As the wavelength decreases, the spreading of the wave at the edges of the aperture also diminishes => the waves will spread out less
*December 20, 2012*

**PHYSICS**

F•Δt=Δp=mΔv=m[v₂-(-v₁)]=m(v₂+v₁) m= F•Δt/ (v₂+v₁)=540•6.9•10⁻³/(42+20) = 0.06 kg
*December 19, 2012*

**Physics**

V=7.5 m/s v=1.52 m/s u=? u(x)=V(x)+v(x)= 0-vsin42⁰= - 1.52•0.67=-1.02 m/s u(y)=V(y)+v(y)= V+vcos42⁰=7.5+1.52•0.0.74=8.63 m/s u=sqrt{u(x)²+ u(y)²}=8.69 m/s tanβ = u(x)/u(y)=1.02/8.63=0.12 β =6.74⁰ (west of north)
*December 19, 2012*

**Physics**

Q₁=Q₂ => cm₁(t₁-t) = cm₂(t-t₂) m₁(t₁-t) = m₂(t-t₂) Solve for ‚t“
*December 17, 2012*

**Physics**

a=(v²-v₀²)/2s=v²/2s F=ma
*December 17, 2012*

**Physics**

P=E/t=F•x/t=F•v
*December 17, 2012*

**physics**

m₁ =0.55 kg,t₁ =96.7℃ c₂=4186 J/kg•℃, m₂=2.19 kg, t₂=4.4℃ t= 7℃ Q₁=c₁m₁(t₁-t) Q₂=c₂m₂(t-t₂) Q₁=Q₂ => c₁m₁(t₁-t) = c₂m₂(t-t&#...
*December 17, 2012*

**physics**

m₁ =0.55 kg,t₁ =96.7℃ c₂=4186 J/kg•℃, m₂=2.19 kg, t₂=4.4℃ t= 7℃ Q₁=c₁m₁(t₁-t) Q₂=c₂m₂(t-t₂) Q₁=Q₂ => c₁m₁(t₁-t) = c₂m₂(t-t&#...
*December 17, 2012*

**Pysics**

m₁ =0.55 kg,t₁ =96.7℃ c₂=4186 J/kg•℃, m₂=2.19 kg, t₂=4.4℃ t= 7℃ Q₁=c₁m₁(t₁-t) Q₂=c₂m₂(t-t₂) Q₁=Q₂ => c₁m₁(t₁-t) = c₂m₂(t-t&#...
*December 17, 2012*

**physics**

efficiency of Otto engine is e= 1 –{V₂/V₁}^(γ-1) γ=(i+2)/i For diatomic gas i=5 =>γ=7/5=1.4 V₁/V₂= CR (compression ratio) e= 1 –{1/CR}^(γ-1)=1-{1/CR} ^0.4 0.331 = 1-{1/CR} ^0.4 Solving for CR, we obtain CR=2.73
*December 17, 2012*

**physics**

CoP=4.5 CoP=Qh/(Qh-Qc)=1/{1-(Qc/Qh)}=4.5 Qc/Qh=0.78 Qc=46.1 cal Qh= Qc/0.78 = 46.1/0.78=59.1 cal
*December 17, 2012*

**physics**

c₁=129 J/kg•℃, m₁ =2.6 kg,t₁ =90℃ c₂=4180 J/kg•℃,m₂=0.21 kg, t₂=23℃ t=? Q₁=c₁m₁(t₁-t) Q₂=c₂m₂(t-t₂) Q₁=Q₂ => c₁m₁(t₁-t) = c&#...
*December 17, 2012*

**physics**

F= mv²/R
*December 17, 2012*

**physics**

Q=cm(t₂-t₁) Q= 1502 J, m=0.032kg, t₁=29℃ c=387 J/kg•℃ Solve for t₂
*December 17, 2012*

**physics**

Increasing the wavelength of the light, Changing the metal, Decreasing the frequency of the light
*December 17, 2012*

**science**

a=F/m
*December 16, 2012*

**science**

Incomplete question
*December 16, 2012*

**physics**

Points: left end - A, Sam - B, center of mass - C , Joe - D , right end - E Torques about the point B: mg•BC –F(J) •BD =0 F(J) =mg•BC/BD= 430•2.8/4.6 = 261.7(N) Torques about the point D F(S) •BD - mg•CD = 0 F(S)= mg•CD/BD = 430•1.8...
*December 16, 2012*

**Physics**

m=W/g=W1/g1 g1=g•W1/W
*December 16, 2012*

**physics**

W=KE₂-KE₁=mv₂²/2 -mv₁²/2= =0.5m(v₂² - v₁²) Law of conservation of angular momentum I₁ω₁=I₂ω₂ (m₁ r₁²)(v₁/r₁)=(m₂ r₂²)(v₂/r₂) v&#...
*December 16, 2012*

**physics**

KE2-KE1=W(fr) =F•s mv₂²/2 - mv₁²/2 = F•s Solve for F
*December 16, 2012*

**science**

Please see the Related Questions below
*December 16, 2012*

**Physics**

W₀=mg g=GM/R². W=mg´, g=GM/(R+h)² ΔW= W₀-W 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.
*December 16, 2012*

**Physics**

ω₀=2πn₀=2π•2000/60 rad/s ω=2πn =2π•150/60 rad/s ω=ω₀-εt ε= (ω₀-ω)/t=…. L₀=I ω₀=… L=I ω=… L(ave) =(L+L₀)/2
*December 16, 2012*

**physics**

ma= F(fr)= μN =μmgcosα a= μgcosα
*December 16, 2012*

**physics**

L=Iω I(hoop) =mR² I(sol.cyl)= mR²/2 I(sol.sph) =2 mR²/5 I(hol.sph) =2 mR²/3
*December 15, 2012*

**Physics**

E=mc²=320•10⁻⁶•9•10¹⁶=2.88•10¹³ J E/3.65•10⁷=2.88•10¹³ /3.65•10⁷=7.9•10⁵ L 7.9•10⁵•12.75=1•10⁷ km
*December 15, 2012*

**Physics**

v(n+1) = {v´+v(n)}/{1+(v´•v(n)/c²} v2= {v´+v1}/{1+(v´•v1/c²}= ={0.5c+0.5c}/{1+(0.5c•0.5c/c²} =0.8c. v3={0.8c+0.8c}/{1+(0.8c•0.8c/c²}...0.929 c v4=...=0.97561c, v5=...= 0.9918c v6=...=0.99726c, v7=...=0.99909c > 0....
*December 15, 2012*

**Physics**

0= - mg+N+Fsinα => N=mg-Fsinα => F(fr) =μN =μ(mg-Fsinα) ma=Fcosα-F(fr) = Fcosα - μ(mg-Fsinα) a=0 Fcosα =μmg- μFsinα F(cosα + μsinα)=μmg F= μmg/(cosα + μsinα)= …
*December 15, 2012*

**Physics**

0= - mg+N+Fsinα => N=mg-Fsinα => F(fr) =μN =μ(mg-Fsinα) ma=Fcosα-F(fr) = Fcosα - μ(mg-Fsinα) a=0 Fcosα =μmg- μFsinα F(cosα + μsinα)=μmg F= μmg/(cosα + μsinα)= …
*December 15, 2012*

**physics**

(a) p=mv km/h -> m/s !!! (b) F=ma=mv/t
*December 15, 2012*

**Physics**

rest energy of electron m₀c²=0.512 MeV E=mc²=1533 MeV mc² =m₀c²/sqrt(1-β²)... (1) τ=τ₀/sqrt(1-β²) …..(2) Divide (1) by (2) mc²/τ= m₀c²/τ₀ τ₀=τ• m₀...
*December 15, 2012*

**physics**

t=sqrt(2h/g) L=v• t
*December 15, 2012*

**Physics**

ma=mgsinα –F(fr) = mgsinα – μmgcosα a= g(sinα – μcosα ) = 9.8• (0.59-0.16•0.81)=4.5 m/s² The speed after the first 5 sec is v=at= 4.5•5=22.5 m/s If the net force=0, a=0 => 0 = mgsinα – μ&#...
*December 15, 2012*

**science**

(a) V=2.68 L = 0.00268 m³, t=37°C => T=310 K, p=743 torr =99058.246 Pa R=8.31 J/mol pV=nRT n= pV/RT = 99058.246•0.00268/8.31•310 =0.1 mol N= n•N₀=0.1•6.02•10²³=6.02•10²² molecules (b) V=5•10³ L=5 m...
*December 15, 2012*

**Physics**

Fick’s Law M= -D•(Δρ/Δx)•A, where M = m/t = mass flux [kg/s], D= 4.9•10 ⁻⁹ m ²/s is the diffusion coefficient (diffusivity) [m²/s], Δρ/Δx is the gradient of density [kg/m⁴], A is the area [m²]. ...
*December 15, 2012*

**physical science**

v₁= {-2m₂v₂₀ +(m₁-m₂)v₁₀}/(m₁+m₂) v₂={ 2m₁v₁₀ - (m₂-m₁)v₂₀}/(m₁+m₂)
*December 15, 2012*

**Physics**

The law of conservation of angular momentum L₁ = L₂ {(MR²/2) +(mR²)}ω₁ ={(MR²/2) +(mr²)}ω₂ ω₂=ω₁{(MR²/2) +(mR²)}/{(MR²/2) +(mr²)}= =2{60•4/2 + 32•4}/(60•4/2+ 32•...
*December 14, 2012*

**physics**

Doppler effect Frequency (observed) f=c/λ=3•10⁸/5.87•10⁻⁷=5.11•10¹⁴ Hz Frequency (apparent) f´=c/λ´=3•10⁸/5.9•10⁻⁷=5.085•10¹⁴ Hz f'=cf/(c+u) u=c{(f/f´)-1} =1.53...
*December 14, 2012*

**physics**

I = P/A = P/4πr² = 100/4π(8)² = 0.12 W•m⁻² If the sound intensity level is halved to a value of I = 0.06 W•m⁻², the sound intensity level will decrease by 3 dB. I = P/4πr² = 100/4π(x) ² = =0.06 W•m&#...
*December 14, 2012*

**physics**

F=mg g=F/m=236/63=3.746 m/s² h=gt²/2 t=sqrt(2h/g)=sqrt(2•2.1/3.746)=1.06 s.
*December 14, 2012*

**physics**

I = P/A = P/4πr² = 100/4π(8)² = 0.12 W•m⁻² If the sound intensity level is halved to a value of I = 0.06 W•m⁻², the sound intensity level will decrease by 3 dB. I = P/4πr² = 100/4π(x) ² = =0.06 W•m&#...
*December 14, 2012*

**physics**

λ=4L=4•0.9=3.6 m f=v(sound)/ λ
*December 14, 2012*

**physics**

(a) Stretch in the spring is L₁=sqrt(x²+L₀²) = sqrt(0.7² +0.5²)=0.86 m Elongation is Δx= L₁-L₀= 0.86-0.5=0.36 m. E(total) = PE=2•k•Δx²/2=2•37.7•0.36²/2=4.9 J. (b) PE=KE =mv²/2 v=sqrt(2&#...
*December 14, 2012*

**physics**

m1= 443 kg, m2=181 kg, F(fr) = F =G•m1•m2/R², μ•m2•g= G•m1•m2/R², μ•g= G•m1/R², R =sqrt(G•m1/ μ•g).
*December 13, 2012*

**physics**

see the Related Questions below
*December 13, 2012*

**physics**

mg=GmM/R² g=GM/R² g´=GM/(R+h)² g´= 0.337g GM/(R+h)² =0.337• GM/R² R²/0.337=(R+h)²= R²+2Rh+h² h²+2Rh - 1.96R² = 0 h=- R±sqrt{R²+1.96 R²}= =-R±1.72R h=0.72R=0.72•6.38•10⁶...
*December 13, 2012*

**physics**

F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg²,
*December 13, 2012*

**physics**

m1= 443 kg, m2=181 kg F(fr) = F =G•m1•m2/R² μ•m2•g= G•m1•m2/R² μ•g= G•m1/R² R =sqrt(G•m1/ μ•g)
*December 13, 2012*

**Physics**

http://ca.answers.yahoo.com/question/index?qid=20101003132118AAicaXe
*December 13, 2012*

**physics**

v=sqrt(T•L/m) λ=v/f => f=v/λ= sqrt(T•L/m)/ λ f₁/f₂={sqrt(T₁•L/m)/ λ}/{sqrt(T₂•L/m)/ λ} (f₁/f₂)² =T₁/T₂ T₂=T₁(f₂/f₁)² (T₂-T₁)/T₁=(...
*December 13, 2012*

**Physics**

s=v₀t+at²/2, v₀= 4.5 m/s, a= 0.04 m/s², t= 12s
*December 13, 2012*

**Physics**

a=(v-v₀)/t=v/t F=ma
*December 13, 2012*

**physics**

http://ca.answers.yahoo.com/question/index?qid=20110714100031AAk4Hfp
*December 13, 2012*

**Physics**

Find answer in the Related Questions
*December 12, 2012*

**Physics**

C=q/U =Ne/U , N=CU/e=55•10⁻ ¹²•5.3/1.6•10⁻ ¹⁹ =1.82•10⁹
*December 12, 2012*

**Physics**

closed end – node open end - antinode => A quarter of the wavelength is on the length of the pipe => λ=4L=4•0.6 = 2.4 m λ=v/f f=v/ λ=340/2.4 =141.5 Hz
*December 12, 2012*

**Physics**

A) 141.5 Hz
*December 12, 2012*

**physics**

From similar triangles: Hi/di =Ho/do => Hi/Ho=di/do =M
*December 12, 2012*

**physics**

mgh =179 m=179/mg =179/0.296•9.8 = 61.7 kg
*December 12, 2012*

**Physics**

Magnetic field due to the long wire B₁=μ₀I/2πb=4π•10⁻⁷•20/2•π•0.003=1.3•10⁻³ T ( B₁ is directed normal to the axis of solenoid) B=sqrt(B₁²+B₂²) =sqrt{(1.3•10⁻...
*December 12, 2012*

**physics**

PE=kx²/2 k=2•PE/ x²= =2•2.5/0.15²=222 N/m
*December 12, 2012*

**physics**

PE =KE =KE(trans)+ KE(rot) = mgL=mv²/2 +Iω²/2= =m ω²L²/2 + m ω²L²/3•2= =2 m ω²L²/3, ω=sqrt(3g/2L)=sqrt(3•9.8/2•1.2) = =sqrt(12.24)=3.5 rad/s
*December 12, 2012*

**physics**

mg= F =G•m •M/(R+h)² g= G•M/(R+h)² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², h=3600000 m=3.6•10⁶ m Earth’s mass is M = 5.97•10²⁴kg, Earth’s radius is R = 6.378•10&#...
*December 12, 2012*

**Physics**

F(fr)=μ•N=μ•m•g•cosα
*December 11, 2012*

**Physics**

F(fr)=μ•N=μ•m•g μ=F(fr)/mg
*December 11, 2012*

**Science**

The most common mineral of the Earth's continents is quartz, the mineral SiO2.
*December 11, 2012*

**science**

http://en.wikipedia.org/wiki/Ion
*December 11, 2012*

**science**

http://en.wikipedia.org/wiki/Isotope
*December 11, 2012*

**science**

http://www.chem4kids.com/files/elem_pertable.html http://en.wikipedia.org/wiki/Periodic_table
*December 11, 2012*

**science**

http://www.chem4kids.com/files/atom_bonds.html
*December 11, 2012*

**Science**

http://www.chem4kids.com/files/atom_electron.html
*December 11, 2012*

**physics**

μ=0.14, s=30 m=160 kg x: m•a= m•g•sinα - F(fr), y: 0= - m•g•cosα +N. F(fr)=μ•N= μ• m•g•cosα m•a= m•g•sinα - μ• m•g•cosα a= g(sinα - μ•cosα...
*December 11, 2012*

**English**

we are learning about the 14 tenses: past,present,future,past perfect,present perfect, future perfect, past progressive..., past perfect progressive..., emphatic..and then there is another one but i forgot what that one was. Anyway, i need a website that can help me with these...
*December 10, 2012*

**Math**

Christine currently has $5000 in her 401(k) and plans to contribute $100 each month for the next 30 years into it. What will be the value of Christine's 402(k) in 30 years if the per annum rate of return is assumed to be 12% compounded monthly?
*December 10, 2012*

**English**

We are working on Passive and Active voice. i really dont understand it, so do you know any websites that could help me with passive and active voice.
*December 10, 2012*

**math**

i typed it in my calculator and i got : 1910 but i dont know if thats right? sorry
*December 10, 2012*

**Math**

Christine currently has $5000 in her 401(k) and plans to contribute $100 each month for the next 30 years into it. What will be the value of Christine's 402(k) in 30 years if the per annum rate of return is assumed to be 12% compounded monthly?
*December 10, 2012*