Friday
April 29, 2016

# Posts by Elena

Total # Posts: 4,383

Physics
d•sinθ=2k•λ/2=k λ k=4 d•sinθ==4 λ
October 31, 2012

Physics
d•sinθ=2k•λ/2=k λ k=4 d sinθ = 4λ
October 31, 2012

Physics
θ=arcsin(1/n)=arcsin(1/1.501) =41.78°
October 31, 2012

PHYSICS
http://drcarlphysics.wikispaces.com/Week+5,+Group+3+-WA19,Q8
October 31, 2012

physics
d=sqrt(18²+25²)=... tanα=18/25, α= arctsn(18/25)
October 31, 2012

physics
The time of flare falling down t=8 s = > The flare fell from the height h=gt²/2 =9.8•8²/2=313.6 m since the time of accelerated helicopter motion is t1 =25 s, its acceleration was a=2h/t1²= 2•313.6/25²=1 m/s² The helicopter gets off by the...
October 31, 2012

PHYSICS!
W=mg m=W/g=528/9.8=53.88 kg
October 31, 2012

Physics
A. Focal length = half of radius of curvature = > f = 25/2=12.5 cm B. 1/o+1/i=1/f, where o is the object distance, I is the image distance , and f is the focal length, 1/I =1/f-1/o= 1/12.5- 1/40 = > I = 18.2 cm. C. Magnification = 12.5/(40-12.5) = 0.45 D. Height of image...
October 31, 2012

Physics
Its velocity is maximum.
October 31, 2012

Physics
32.04 r=sin⁻¹(sini/n)
October 31, 2012

Physics
The path of a light ray that crosses the boundary between two different media is irreversible
October 31, 2012

Physics
Light cannot be linearly polarized by: A transmission B reflection C diffraction D scattering D
October 31, 2012

Physics
t=sqrt(2h/g) v= gt=sqrt(2gh)
October 31, 2012

physics
http://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion
October 31, 2012

physics
http://hyperphysics.phy-astr.gsu.edu/hbase/kepler.html
October 31, 2012

m1•a=F-T-m1•g•sinα m2•a=T (m1+m2)a= F-T-m1•g•sinα+T a=(F-m1•g•sinα)/(m1+m2). T=m2•a=m2• (F-m1•g•sinα)/(m1+m2)=...
October 31, 2012

physics
E+PE1 =PE2 E=PE2-PE1=m•g•h2 -m•g•h1 = =m•g•s2•sinβ- m•g•s1•sinα = =m•g•( s2•sinβ -s1•sinα )= =3.5•9.8•(16•sin69.3 - 6•sin28.9) =402 J
October 31, 2012

physics
mg=Tcosα cosα=mg/T PE=KE PE= mgh=mgL(1-cosα) KE= mv²/2 mv²/2=mgL(1-cosα) v=sqrt{2gL(1-cos α)}= sqrt{2gL(1- mg/T)}=…
October 31, 2012

physics
Without air resistance KE=PE mv²/2=mgh h=v²/2g =27²/2•9.8 = 37.2 m (mgh-mgh1)/mgh = (h-h1)/h= (37.2-16.3)/37.2=0.56 56%
October 31, 2012

Physics HELP!!
ma=-mg+T T=m(a+g) = 7.37(3.62+9.8) =…
October 31, 2012

Physics HELP!!
(a) ma=F1+F2 =0 F2=F1 = 27.56 N (b)ma=F1+F2 1.11•(-9.3) = 27.56 +F2 F2= -37.883 N
October 31, 2012

physics
sinθ =R(cutting surface)/R(cutting tool) =4/40 =0.1 θ=sin⁻¹0.1 =5.7°
October 31, 2012

Physics
(a) M= F•W =46.6•1.26 = ... (b) M= F•W•sinα =46.6•1.26 •sin43°= (c) M=0
October 30, 2012

Physics
c•m1• (t-25) = c•m2• (75-t) 80t - 80•25 =150•75- 150t 230t= 13250 t=57.6°
October 30, 2012

Physics
This ball fell during t=sqrt2h/g) =sqrt(2•0.9/9.8)=0.43 s Horizontal motion (v(x)=const) => L=v(x) •t v(x)=L/t=2.6/0.43=6.1 m/s
October 30, 2012

Physics
ma=μmg a=μg v=v₀-at=v₀-μgt=...
October 30, 2012

Physics
PE=KE=KE(transl)+KE(rot) m•g•h=m•v²/2 +I•ω²/2 ω=v/R disc I=m•R²/2 => I•ω²/2= m•R²•v²/2•2• R²=m•v²/4 . m•g•h=m•v²/2 + m•v²/4=0.75 m&#...
October 30, 2012

Physics
T=2π/ω
October 30, 2012

college physics
L=vₒ²•sin2α/g, solve for 'v'
October 30, 2012

ma=F(grav) mv²/R =GmM/R² G •ρ•4πR³/3• m/R² =m(v²/R) R=sqrt{3v²/4πρG}=... M = ρ•4πR³/3= …. T=2π/ω=2πR/v=....
October 29, 2012

(a) ω₃=ε•t₃ =0.65•3 =1.95 rad/s (b) ma=F(fr) centripetal acceleration a=v²/R =ω²R F(fr) =μmg m ω²R= μmg ω=sqrt(μg/R)=sqrt(0.42•9.8/0.18)=4.78 rad/s (c) ω =ε•t t= ω/ε=4.78...
October 29, 2012

A full- length recording lasts for 74 min, 33 s , t=74 min33 sec =4473 s ω1=v/R1 =1.22/0.021 = 58.1 rad/s ω2=v/R2 =1.22/0.061 = 20 rad/s ε= (ω2- ω1)/t =(20-58.1)/ 4473=-0.0085 rad/s² φ=εt²/2=0.0085•4473²/2=85032.8 rad L=v...
October 29, 2012

t=74 min33 sec =4473 sá ω1=v/R1 =1.22/0.021 = 58.1 rad/s ω2=v/R2 =1.22/0.061 = 20 rad/s ε= (ω2- ω1)/t =(20-58.1)/ 4473=-0.0085 rad/s²
October 29, 2012

Physics, newtons laws
v₀=sqrt{v₀² (x) +v₀²(y)}= =sqrt{86.6²+50²} = =100 m/s. tan α= v₀(y)/v₀ (x)=50/86.6 α= tan ⁻¹(50/86.6) =30° t= 2vₒ•sinα/g
October 29, 2012

Physics, newtons laws
x: ma=Tsinα y: mg=Tcosα ma/mg =Tsinα/ Tcosα a/g =tanα v²/R•g =tanα α=tan⁻¹(v²/R•g) = …
October 29, 2012

physics
If the carton is moved at uniform velocity ma=0 F-F(fr) –mgsinα = 0 F= F(fr) +mgsinα =μmgcosα+ mgsinα = =mg (μ•cosα + sinα)
October 29, 2012

n₀=3500 rev/min =3500/60 rev/s =58.33 rev/s N= 41 rev, (a) ω=2π•n₀=2π•58.33=366.5 rad/s (b) φ =2π•N =2π•41 =257.6 rad (c) φ= ω²/2•ε, ε= ω²/2•φ=58.33²/2•257...
October 29, 2012

physics
If the carton is moved at uniform velocity ma=0 F-F(fr) –mgsinα = 0 F= F(fr) +mgsinα =μmgcosα+ mgsinα = =mg (μ•cosα + sinα)
October 29, 2012

PE(spring) =PE + W(fr) k•x²/2 =m•g•(2R) +μ•m•g•s. x= sqrt{2(m•g• 2R +μ•m•g•s)/k} = = sqrt{2m•g• (2R +μ•s)/k}= =sqrt{2•0.5•9.8(3.2 + 0.3•2.2)/84.8}= =0.668 m
October 29, 2012

physics
(a)W(gravity) = mgh (b) mgh =mv²/2 v=sqrt(2gh) (c) the same (d) mgh = W(fr) + mv1²/2 v1 <v
October 29, 2012

Physics
mgh =mv²/2 v=sqrt(2gh) = sqrt(2•9.8•5.6) = 10.5 m/s Correct further calculations...
October 29, 2012

Physics
(a) The law of conservation of energy: PE=KE mgh =mv²/2 v=sqrt(2gh) = sqrt(2•9.8•5) = 9.9 m/s m1==> v1 =+9.9 m/s m2 ==> v2 = - 9.8 m/s (b) the law of conservation of linear momentum: After elastic collision u1 = [(m1 - m2)/(m1 + m2)]•v1 + [ 2 •m2...
October 29, 2012

Physics
i1 =10A, i2 =1A sde a=10cm=0.1 m, distance between the straight cureent and the side 12 of the loop is b=10 cm =0.1 m Assume that the directions of the currents are following : i1↑I ⃞ ↓i2 Points 1,2,3, and 4 are located clockwise starting from the left bottom...
October 29, 2012

Physics
red and green
October 29, 2012

Physics
light reflected from the surface of a dry asphalt roadway
October 29, 2012

physics
The guage pressure at the height h = ρgh the atmospheric pressure = 1.013•10⁵ Pa ρgh•760/1.013•10⁵ =1030• 9.8•0.61•760/1.013•10⁵=46.2 mmHg
October 28, 2012

phisics
(a) ΔKE=ΔPE KE(B)-KE( A)=PE(A)-PE(B) mv²/2 -0 =mgh(A)-mgh(B) v=sqrt{2g[h(A)-h(B)]} (b) KE1/KE2 = {m1•gh(A)-mgh(B)}/ {m2•gh(A)-mgh(B)} = =m1/m2
October 28, 2012

Physics help
ma=F-F(fr) a=[F-F(fr)]/m s=at²/2
October 26, 2012

Physics
ω₀=2πn₀=2π/33.2=0.19 rad/s centripetal acceleration is a(cen) = ω₀²R=0.19²•42.2=1.52 m/s² tangential acceleration is a(tan) =ε•R =0.0542•42.2=0.12 m/s² acceleration is a=sqrt{ a(cen)²+a(tan)&#...
October 26, 2012

Physics
Man: φ =ω•t Dog: φ –π/2=ε•t²/2 ω•t= ε•t²/2 +π/2 ε•t² -2 ω•t+π=0 t={2±sqrt(4-2•3.14•0.31}/2•0.31 t1=3.74 s, t2 = 1.48 s ω(dog) = ε•t=0....
October 26, 2012

Physics
Man: φ=ω•t Dog: φ=ε•t²/2 ω•t= ε•t²/2 t=2 ω/ ε=2•0.5/0.31 =3.23 s ω(dog) = ε•t=0.31•3.23= 1 rad/s
October 26, 2012

R=4.3 m, a(τ)=8.8 m/s². a(τ)=a(c) =v²/R => v=sqrt{a(c) •R}= sqrt{a(τ) •R}= =sqrt{8.8•4.3}=6.15 m/s. v=a(τ) •t, t= v/a(τ)=6.15/8.8 =0.699 s= 0.7 s. s= a(τ) •t²/2 =8.8•0.7²/2=2.156 m.
October 25, 2012

Physics
13.3 cm
October 25, 2012

Physics
angle of incidence = 30o angle of reflection = 60o angle between incident ray and reflected ray = 120o
October 25, 2012

physics
α=arctan(Fy/Fx)=arctan(60/40)=arctan 1.5=56.3°
October 25, 2012

Physics
y: mg=T+N x: F(fr)=T N=mg-T F(fr)= μN=μ(mg- T) = μmg-μT =T T(1+μ)= μmg T= μmg/(1+μ)=0.49•710/1.49=233.5 Newtons
October 25, 2012

Physics
2•T•sinφ=2•19.5•sin16º=10.75 N
October 25, 2012

Physics!
F(x) =F1(x) +F2(x) F(x)= 57•cos30°+57•cos60° = F(y) =F1(y) +F2(y) F(y) =57•sin30°+57•sin 60° = F=sqrt{F(x)²+F(y)²} tan θ=F(y)/F(x) F(x) =F1(x) +F2(x) +F3(x) =0 57•cos30°+57•cos60° +F3(x) =0 F(y) =F1(y) +F2(y...
October 25, 2012

Physics
Initial heights of the blocks: m1 -> H; m2 -> h Initial energy of the “two blocks” system is E1 = m1•g•H+m2•g•h When the blocks covered s=0.9 m the energy of ”two blocks+spring” system is E2= m1•g(H-s•sinα) +m1•...
October 25, 2012

Physics
0.73 Tesla
October 25, 2012

Physics
Electrons are emitted with more velocity.
October 25, 2012

Physics
The atomic number increases by one.
October 25, 2012

Physics
Both the number of emission of electrons and the maximum velocity will increase.
October 25, 2012

Physics
1.103 m
October 25, 2012

ΣF(x) =F1(x) +F2(x) +F3(x) =0 0+42•cos60°+F3(x) =0 F3(x) = -42•cos60°= -21 N ΣF(y) =F1(y) +F2(y) +F3(y) =0 36+42•sin60°+F3(y) =0 F3(y) =-36 -42•sin60°= -72.4 N F=sqrt{F(x)²+F(y)²} tan θ=F(y)/F(x)
October 25, 2012

Physics
F=mv²/R m=FR/ v²
October 25, 2012

Physics
(m1+m2)a=F m1+m2 =F/a m2=F/a – m1
October 25, 2012

physics
change of current
October 25, 2012

physics
h=g•t²/2 t=sqrt(2•h/g) S=v(x) •t
October 25, 2012

physics
KE=W(fr) KE = m•v²/2 W(fr) =F(fr) •s m•v²/2 =F(fr) •s F(fr)= m•v²/2•s
October 25, 2012

physics
m1=130/9.8 kg , m2=63/9.8 = m1•a=0=T-F(fr) m2•a=0= m2g-T => T=m2•g F(fr) =T =m2•g
October 25, 2012

Physics
v=2πR/t = … a= a(n) =mv²/R F=ma
October 25, 2012

High School Physics
L=vₒ²•sin2α/g, sin2α=L•g/ vₒ²=126•32.174/98²=0.42 1) 2α=25° , α=12.5° 2) 2α =25+90=115°,, α=57.5° t= 2vₒ•sinα/g=...
October 25, 2012

Physics
m₀=ρV=ρ•πD³/6 ρ =920 kg/m³, D=0.021 m
October 24, 2012

Physics
mgh =mv²/2 v²= 2gh) = 2•9.8•10 =196 m²/s² a=v²/2•s =196/2•2.7=36.3 m/s² F(fr) = ma=69•36.3 =2504.7 N
October 24, 2012

physics
KE=PE KE=mgh h=KE/mg =50/0.55•9.8 =9.28 m
October 24, 2012

Physics- Projectiles
h= vₒ²•sin²α/2g,
October 24, 2012

physics college
Forward force = T•cosα
October 24, 2012

physics
Units????
October 24, 2012

Physics
m1•g=N+T m2•g=T m1•g=N+ m2•g N=(m1-m2)g
October 24, 2012

Physics
PE=KE + W(fr) mgh =mv²/2 + F(fr)•s m•g•s•sinα =mv²/2 +μ•m•g•cosα•s Solve for μ
October 24, 2012

Physics
m1 =4.3•10^-3 kg, m2 = 22.6•10^-3 kg, h =1.4 m, L= 3.1 m., v1 =? m1 •v1 = (m1+m2) •v, v= m1 •v1 /(m1 + m2) . h =g•t²/2 => t = sqrt(2•h/g) L= v•t = v• sqrt(2•h/g), v =L/sqrt(2•h/g), m1 •v1 /(m1 + m2) = L/sqrt(2...
October 24, 2012

Physics HELP!!
F(x) =F1(x)+F2(x)+F3(x) =0+19.9 +0 =19.9 N F(y) =F1(y)+F2(y)+F3(y) =11.1+0-14=-3 N F=sqrt{F(x)^2 + F(y)^2} a=F/m tan alpha=F(y)/F(x) unknown angle =appha +90 degrees
October 24, 2012

Physics HELP!!
(a) ma=F1-F2 F2=F1-ma (b)F2=F1 (c) -ma=F1-F2 F2=F1+ma
October 24, 2012

Physics
You accidentally got the right answer. Correect solution is following: The Earth makes one revolution (2π) during 1 year => the angular displacement for 5 days is θ= 2π•5/365 = 0.086 rad. The angular velocity of the Earth is ω= θ/t = 0.086/5&#...
October 24, 2012

Physics
If your question is: If a rod is moving at a velocity equal to 1/2 the speed of light parallel to its length, what will a stationary observer observe about its length? The answer is L=L₀•sqrt{1-(v/c)²}=0.866L₀ The length of the rod will decrease.
October 24, 2012

Physics
F=ILBsinα sinα=1 B=F/IL = 2.2/2•1.5 =0.73 T
October 24, 2012

Physics
Electrons are emitted with more velocity. ε(energy of photon) = Work function + KE ε(blue)>ε(green) => KE(blue) >KE(green) => v(blue) > v(green)
October 24, 2012

Physics
The atomic number increases by one.
October 24, 2012

Physics
The atomic number increases by one.
October 24, 2012

Physics
Both the number of emission of electrons and the maximum velocity will increase
October 24, 2012

physics
(a) sin r = sini/n =sin 58°/1.6=0.53 r =32 ° α=180°-58°-32°=90° (b) δ= 58 -32 =26°
October 24, 2012

Physics
Q(t)=Q₀•exp(-t/RC) E~Q² => E=E₀•exp(-2•t/RC) 100-80=20% 0.2•E₀=E₀•exp(-2•t/R•C) ln0.2 =- 2•t/R•C t= - ln0.2• R•C/2 =- (-1.6) •60•90•10⁻⁶/2 =0.0043 s.
October 24, 2012

texas southern university
p1•V1=p2•V2 p2=p1•V1/V2
October 24, 2012

physics/light reflection
(a) sin r = sini/n =sin 58°/1.6=0.53 r =32 ° α=180°-58°-32°=90° (b) δ= 58 -32 =26°
October 24, 2012

physics
Find the solution in Related Questions
October 24, 2012

physics
m1=1.7 kg, m2 =2.4 kg, L=1.29 m. PE=KE m1•g•L=m1•v²/2 v=sqrt(2•g•L) The velocities of the bodies after elastic collision are u1=(m1-m2)v/(m1+m2), u2=2m1v1/(m1+m2) “-“ means the motion in opposite direction
October 23, 2012

PHYSICS H
http://www.physicsclassroom.com/mmedia/newtlaws/efar.cfm
October 23, 2012