Wednesday
April 16, 2014

Posts by Elena


Total # Posts: 4,303

physics
The speeds of the objects after elastic collision are v₁= {-2m₂v₂₀ +(m₁-m₂)v₁₀}/(m₁+m₂) v₂={ 2m₁v₁₀ - (m₂-m₁)v₂₀}/(m₁+m₂)

Physics
3.going down and speeding up

Physics
x: 0 =F-m•g•sinα-F(fr) y: 0=N-m•g•cosα, 0 =F-m•g•sinα-F(fr)= F-m•g•sinα- μ•N= =F - m•g•sinα- μ•m•g•cosα. F = m•g(sinα- μ•cosα)= = 340•(si...

Physics
I believe that t mass of the traffic light is 27.5 kg!!! We choose the coordinate system with positive torques clockwise. The sum of torques ΣM= 0 about the point A ΣM =-T•H+M•g•L•cosθ+m•g•(L/2)•cos θ = 0; -T(3.80 )+ 27.5&...

Physics
n=30000 rpm=30000/60=500rev/s, ω=2πn=2•3.14•500= ... ME=10•10⁶ J =10⁷J KE=Iω²/2 =mR²ω²/2 R=sqrt(2•KE/m• ω²)=… D=2R

Physics
m(hole)= m, M(plate)=M We must treat the holes as the objects of negative mass. The moment of inertia is I=I(plate) – 3I(hole). The plate is disk => I(plate)=M•R²/2. The moment of inertia of the hole using the parallel axis theorem is I(hole)= m•r²/...

Physics
Weight is the force with which the object presses the stationary support. Weight may be less or greater than the force of gravity (mg) in dependence on the downward or upward motion, => Weight = N, but directed in the opposite direction vector (ma)= vector (mg)+vector( N) f...

physics
how much force the floor is pressing up on the crate with F(fr)=μN

physics
sin θ= n(water)/n(glass) n(glass)= n(water)/ sin θ=1.33/sin60.1=1.53

physic
in the wire - 1D (linear waves) in the air -3D(space wave)

Physics
I believe that the refractive index of water is n=1.3 Incidence angle α. sin α =8/sqrt(8²+6)=0.8 sinα/sinβ=n => sinβ= sinα/n =0.8/1.3=0.61 =>β= 38° x=h•tan β=2•tan38°=1.56 m

physics
.."as shown below" ??????????

physic question
kx²/2=mv²/2 v=x•sqrt(k/m) t=sqrt(2h/g) s=v•t= x•sqrt(k/m) • sqrt(2h/g) => s1= x1•sqrt(k/m) • sqrt(2h/g) s2= x2•sqrt(k/m) • sqrt(2h/g) s1/s2=x1/x2 x2=x1•s2/s1 =1.1 (2.15/(2.15-0.23) =1.23 cm

physics
n(relative)=n(glass)/n(air)=n(glass)= =n=1.523 For equilateral prism α=60° n(relative)=sin{½• (α+θ)}/sin(½•α) sin{½• (α+θ)}= n• sin(½•α)=1.583•sin30°=0.7915 ½• (α+θ...

physics
E=500•24•365•24•3600 = ...(J)

physics
Earth’s radius is R = 6.378•10⁶ m. L=Iω=mR²•2•π/24•3600=84•(6.378•10⁶)²•2• π/24•3600=….

Physics
d•sinθ=2k•λ/2=k λ k=4 d•sinθ==4 λ

Physics
d•sinθ=2k•λ/2=k λ k=4 d sinθ = 4λ

Physics
θ=arcsin(1/n)=arcsin(1/1.501) =41.78°

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

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

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...

PHYSICS!
W=mg m=W/g=528/9.8=53.88 kg

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...

Physics
Its velocity is maximum.

Physics
32.04 r=sin⁻¹(sini/n)

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

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

Physics
t=sqrt(2h/g) v= gt=sqrt(2gh)

physics
http://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion

physics
http://hyperphysics.phy-astr.gsu.edu/hbase/kepler.html

physics ..PLEASE HELP ASSIGN DUE SOON :(
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)=...

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

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)}=…

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%

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

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

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

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

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

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

Physics
ma=μmg a=μg v=v₀-at=v₀-μgt=...

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...

Physics
T=2π/ω

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

Physics- Elena please help!
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=....

Physics- Elena please help!
(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...

Physics- Elena please help!
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&...

Physics- Elena please help!
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

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

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) = …

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)

Physics- Elena please help!!!!
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...

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)

Physics- Elena please help!
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

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

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

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...

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...

Physics
red and green

Physics
light reflected from the surface of a dry asphalt roadway

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

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

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

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)...

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=0.3...

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

Physics- PLEASE HELP
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.

Physics
-0.33

Physics
13.3 cm

Physics
angle of incidence = 30o angle of reflection = 60o angle between incident ray and reflected ray = 120o

physics
α=arctan(Fy/Fx)=arctan(60/40)=arctan 1.5=56.3°

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

Physics
2•T•sinφ=2•19.5•sin16º=10.75 N

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...

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•...

Physics
0.73 Tesla

Physics
Electrons are emitted with more velocity.

Physics
The atomic number increases by one.

Physics
Both the number of emission of electrons and the maximum velocity will increase.

Physics
1.103 m

Physics URGENT! PLEASE
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)

Physics
F=mv²/R m=FR/ v²

Physics
(m1+m2)a=F m1+m2 =F/a m2=F/a – m1

physics
change of current

physics
h=g•t²/2 t=sqrt(2•h/g) S=v(x) •t

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

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

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

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=...

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

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

physics
KE=PE KE=mgh h=KE/mg =50/0.55•9.8 =9.28 m

Physics- Projectiles
h= vₒ²•sin²α/2g,

physics college
Forward force = T•cosα

physics
Units????

Physics
m1•g=N+T m2•g=T m1•g=N+ m2•g N=(m1-m2)g

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

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...

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

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