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September 29, 2016

Posts by Elena

Total # Posts: 4,384

physics
I1=m1•r² I2=m2•r² I3=m3•r²
November 7, 2012

Physics HELP!
M= m•g•L•sinα=7.4•9.8•2.1•sin3°=7.97 N•m
November 7, 2012

Physics
Before collision PE=KE m•g•h =m•v²/2 v=sqrt(2•g•h)= v₁₀=v₂₀=sqrt(2•9.8•5.8)=10.7 m/s (b) After collision v₁= {-2m₂•v₂₀ +(m₁-m₂)•v₁₀}/(m₁+m₂...
November 7, 2012

Physics
When the objects are moving in opposite directions v₁= {-2m₂•v₂₀ +(m₁-m₂)•v₁₀}/(m₁+m₂) v₂={ 2m₁•v₁₀ - (m₂-m₁)•v₂₀}/(m₁+m₂)
November 7, 2012

Physics
On the Earth mg=GmM/R² In the spacecraft mg'=GmM/(5R)²= {GmM/R²}/25=mg/25 His weight is 50.0/25 =2.0 N
November 7, 2012

Physics
tan α=ma₁/mg = (mv₁²/r)/mg= v₁²/rg tan β=ma₂/mg = (mv₂²/r)/mg= v₂²/rg tan α/ tan β= v₁²/v₂² v₂ = v₁•sqrt(tan β/tan α)=18.5•sqrt(tan16/tan11)= =22....
November 7, 2012

physics
Q=c•m•ΔT For brass c= 385 J/kg•K ΔT= Q/c•m=760/385•1=1.97º
November 7, 2012

physics
Q=c•m•ΔT For brass c= 385 J/kg•K ΔT= Q/c•m=760/385•1=1.97º
November 7, 2012

physics
KE of the objects transforms into PE, and then PE→KE => v(start) =v(land)
November 7, 2012

Physics
F(fr) =2•μ•N=m•v²/R R= m•v²/2•μ•N=6•10⁻³•17²/2•0.73•1.8 = …
November 7, 2012

Physics Help!
β = ΔV/V•ΔT β =10•10⁻⁴(1/℃) ΔV=β•V•ΔT=10•10⁻⁴43.3•10⁻³•(34.5-14.5)=8.66•10⁻⁴ m³=0.866 liter.
November 6, 2012

Physics Help!
Linear expansion coefficient α=ΔL/L•ΔT For steel α =12•10⁻⁶ (1/℃) ΔL=α• L •ΔT= =12•10⁻⁶•514•(32.7+20.3)=0.327 m
November 6, 2012

physics
r= v²/a
November 6, 2012

Physics B
F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², R= 0.241 m F13= G•m1•m3/R² F23= G•m2•m3/R² F23-F13= =G •m3• (m2-m1)/R²= =6.67•10⁻¹¹•41.1&#...
November 6, 2012

Physics
T=2•π•r/v=2•π•sqrt(r³/GM) T1=T2
November 6, 2012

physics
T2=mg/sin52 =57/0.788=72.3 N T1 = T2cos52=72.3•0.616= 44.5 N
November 6, 2012

physics
F(fr) =μ(s) •m•g•cosα
November 6, 2012

physics
T=F(fr) =μ(s) •m•g
November 6, 2012

physics
0=v₀-at a=v₀/t s=at²/2
November 6, 2012

physics
v=at
November 6, 2012

Physics B
F =G•m1•m2/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², R= 0.241 m F13= G•m1•m3/R² F23= G•m2•m3/R² F23-F13= =G •m3• (m2-m1)/R²= =6.67•10⁻¹¹•41.1&#...
November 6, 2012

physics
a=(v-v₀)/t=- 42/0.014=3000 m/s²
November 6, 2012

Physics- PLEASE HELP
http://www.mathematische-basteleien.de/ladder.htm Problem #7
November 6, 2012

Physics- PLEASE HELP
L•sinθ
November 6, 2012

physics
vector T +vector mg +vector F(el) =0 x: -T+F(el)cos37 =0 y: Fsin37 –mg =0 F(el) =qE q•E•cos37 = T q•E •sin37 =mg tan37 =mg/T T=mg/tan37= ... E=T/q•cos37=...
November 6, 2012

physics
(a) T= m1•g + F(el)= m1•g+ k•q1•q2/r²= =7.5•10⁻³•9.8 + 9•10⁹•32•10⁻⁹•58•10⁻⁹/0.02²=… (b) T1= m1•g + F(el)= m1•g+ k•q1•q2/r1²= T1=0.18 N. ...
November 6, 2012

Physics
T1=m1•a=1•7.885 = 7.885 N
November 6, 2012

Physics
For m1: m1•a=T1 (block m1=1 kg is on the surface ) For m2: m2•a=m2•g – T2 (m2=9 kg) For pulley: I•ε = M => I•a/R= (T2-T1)R => (T2-T1) = I•a/R² a(m1+m2+ I/R²)=m2•g a= m2•g/(m1+m2+ I/R²) =9•9.8/{1+9+(0.3...
November 6, 2012

Physics
For m1: m1•a=T1 For m2: m2•a=m2•g – T2 For pulley: I•ε = M => I•a/R= (T2-T1)R => (T2-T1) = I•a/R² a(m1+m2+ I/R²)=m2•g a= m2•g/(m1+m2+ I/R²) T1= m1•m2•g/(m1+m2+ I/R²) T2 = m2•g -m2•...
November 6, 2012

Physics HELP!
http://www.physics.umd.edu/~richman/phys141/hw8.pdf
November 6, 2012

Physics HELP!
The law of conservation of angular momentum I₁•ω₁ = I₂•ω₂ I₁ =mR²/2, ω₁ = 5.1 rad/s I₂ = mR²/2 +m₀•r². ω₂ = ? (mR²/2) • ω₁=(mR²/2 +m₀•r...
November 6, 2012

Physics HELP!
The law of conservation of angular momentum I₁•ω₁ = I₂•ω₂ I₁ =mR²/2, ω₁ = 5.1 rad/s I₂ = mR²/2 +m₀•R². ω₂ = ? (mR²/2) • ω₁=(mR²/2 +m₀•R...
November 6, 2012

Physics- PLEASE HELP
KE(tr) =m•v²/2, KE(rot) = I•ω²/2 =m•R²•v²/2•2• R²=m•v²/4. KE= KE(tr)+ KE(rot)= =m•v²/2 + m•v²/4= 3• m•v²/4.
November 6, 2012

Physics
M = I•ε I=M/ε
November 6, 2012

Physics- Elena please help!
Nnewton’s 2 Law for rotation M = I•ε, where angular acceleration ε=0.87 rad/s², the torque M = F•R , the moment of inertia I=mR²/2 , F•R= m•R²•ε/2, m=2•F/R•ε=2•180/0.45•0.87=919.54 kg I=mR&#...
November 6, 2012

Physics- Elena please help!
x=(m1•x1+m2•x2+m3•x3+m4•x4)/(m1+m2+m3+m4) = 0+0+3•4+5•x4/ 22 = 0 y=( m1•y1+m2•y2+m3•y3+m4•y4)/(m1+m2+m3+m4) = 0+3•5+0+5•y4/22 =0 12+5•x4 = 0 => x4 = - 2.4 m 15+5•y4 =0 => y4= - 3 m
November 6, 2012

physical science
ΔPE=KE mgΔh=mv²/2 v=sqrt(2gΔh) (a) Δh=5 m, (b) Δh=7.5 m.
November 6, 2012

Physics
You must know the directions of the forces
November 6, 2012

help one question
moonquakes. http://www.wcskids.net/grissom/staff_websites/fleming/Textbook%20pdfs/Space%20text%20pdfs/Chapter%207%20-%20Earth,%20Moon,%20Sun%20System.pdf
November 6, 2012

physics
Electric flux through the sphere with the point charge in its center is Φ = q/ε₀, the area of this sphere is A = 4πr². If the area of the spherical segment is A1=2πr(r-h) Then, from the proportion: q/ε₀ ….. 4πr². Φ1...
November 6, 2012

science
V=mass/density
November 6, 2012

Physics... URGENT !!!!
mg=66700 N, m=66700/9.8 kg, s= 418 m, v ₀=66.5 mph =29.7 m/s v=28.9 mph=12.9 m/s, h=13.1 m KE1-KE2= W(dr)+ PE m•v₀²/2 - m•v²/2= F(dr) •s +m•g•h Solve for “F(dr)”
November 6, 2012

physics
F= m•v²/R
November 6, 2012

Physics
(a) ω=2π/24•3600 rad/s v= ω•R=... a=ω²R=… (b) r=R•cos42° v1= ω•r=... a1=ω²r=…
November 6, 2012

Physics
θ=29°=0.5 rad The angular displacement θ=ω•t=(v/R) •t => t=θ•R/v OA=v•t=v• θ•R/v= θ•R=0.5•3.6=1.8 m
November 6, 2012

physics
ω=ε•t ε=ω/t=100/10=10 rad/s² M=I•ε=(m•R²/2) • ε= 1•0.2²•10/2=0.5 N•m
November 6, 2012

physics
ω=ε•t ε=ω/t M=I•ε=(m•R²/2) • ε=…
November 6, 2012

physics
mg=kx k=mg/x=760/0.5•10⁻³=... mgh=mv²/2 mv²/2=kx²/2. mgh=kx²/2. x=sqrt(2mgh/k)
November 5, 2012

physics
http://www.jiskha.com/display.cgi?id=1351542188
November 5, 2012

Physics
N1=500, U1 = 120 V, U2 = 24V N2=N1•U2/U1= 500•24/120 =100
November 5, 2012

physics
mg=55.5•9.8 =...
November 5, 2012

Physics
vector m•a=vector m•g +vector F(spring) a=0 => 0=vector m•g +vector F(spring) x: 0 = m•g•sinα –k•x, x=m•g•sinα/k=6.1•9.8•sin 39°/126 =0.3 m
November 5, 2012

physics
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.
November 5, 2012

physics
If polarized light of intensity I₀ is incident on a polarizing sheet, the intensity transmitted by the sheet depends on the angle between the polarization direction of the light and the transmission axis of the sheet, φ, via I= I₀•cos²φ. After ...
November 5, 2012

physics HELP
F=ma F=F(fr)=> ma=μmg μ=a/g
November 5, 2012

Physics
V(pool) =π•D²•h/4 V= π•d²•vt/4 π•D²•h/4= π•d²•vvt/4 t=D²vh/d²•v
November 5, 2012

Physics
Centripetal acceleration a=ω²•R=T/m R=T/m•ω² The law of conservation of angular momentum I• ω²=I₀•ω₀² ω=(I₀/I)•ω₀²=(R₀²/R²)•ω₀ R³=(m&#...
November 5, 2012

Physics
m=7,45 g, m1=1220 g, m2=1603 g, v=348 m/s, v1 = 0.648 m/s The law of conservation of linear momentum for the 1st collision m•v+0=m1•v1+m•u u=(m•v-m1•v1)/m = v –(m1/m)v1= 348 – (1220/7.45) •0.648 = 241.9 m/s, The law of conservation of ...
November 5, 2012

physics
What is direction of initial velocity? If v=5 m/s is downward velocity, PE+KE1=KE2 mgh+mv1²/2 =mv2²/2 v2 =sqrt(2gh+v1²)
November 5, 2012

physics
The question is.....???
November 4, 2012

phisics
m=7,45 g, m1=1220 g, m2=1603 g, v=348 m/s, v1 = 0.648 m/s The law of conservation of linear momentum for the 1st collision m•v+0=m1•v1+m•u u=(m•v-m1•v1)/m = v –(m1/m)v1= 348 – (1220/7.45) •0.648 = 241.9 m/s, The law of conservation of ...
November 4, 2012

College Physic
If the inclined plane is not frictionless, you have to know the coefficient of friction. If it is frictionless, then PE=KE=KE(transl) +KE(rot) mgh= mv²/2 + Iω²/2. I=mR²/2, ω=v/R mgh= mv²/2 + mR² v²/4 R²= = 3mv²/4 v=sqrt(4gh/3)
November 4, 2012

physics
x3=7•cos30=6.06 m, y3=7/2 =3.5 m. x=(m1•x1+m2•x2+m3•x3)/(m1+m2+m3) = =0+0+69•6.06/104 =4.022 m. y=( m1•y1+m2•y2+m3•y3)/(m1+m2+m3) = =0+21•7+69•3.5/104 =3.74 m.
November 4, 2012

physics
W=W(fr)= μ•m•g•s
November 4, 2012

Physics
The torque is M=F•cosα•L. The ball is material point => its moment of inertia is I=m•L². The Newton’s 2 law for rotation M=I•ε, F•cosα•L= m•L²•ε, ε= F•cosα•L/ m•L²=F&#...
November 4, 2012

physics
20.7-2.25=18.45 cm Effort x Effort-arm = Load x Load-arm Load is 18.45 29.3/2.25=…
November 4, 2012

Physics
s=v₀•t+a•t²/2 Solve for v₀
November 4, 2012

physics
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.
November 4, 2012

Physics Help, Please
m•a=F(fr)=μ(s)•m•g a= μ(s)•g
November 4, 2012

Physics
N = mg+Fsinα = 14•9.8 +200•sin37
November 4, 2012

physics
The torques: m(A) •g•2 +(m/2) •g•1 = =(m/2) •g•1+m(B) •g•2+m(C) •g•x 2{m(A)-m(B)}=m(C) •x x=2(42-26)/21 = 1.52 (meters)
November 4, 2012

physics
m1•0+m2•v2=(m1+m2)v v=m2•v2/(m1+m2)
November 4, 2012

physics
T=2•π•sqrt(l/g) T= 2•π•sqrt(m/k) sqrt(l/g) =sqrt(m/k) L/g=m/k Solve for ‚m’.
November 4, 2012

physics
Let V be the volume of the duck. Weight of displaced water = weight of the duck 0.26•V•ρ•g= mg 0.26•V•1000•g =mg 260 V = m The density of the duck is ρ= m/V= 260 V/V= 260 kg/m³ V= m/V=2.6/260=0.01 m³
November 4, 2012

physics
v₁= (m₁-m₂)v₁₀/(m₁+m₂) v₂=2m₁v₁₀ /(m₁+m₂)
November 4, 2012

Physics
2) 8.8 m/s2 m•a=F(fr)=μ(s) •m•g a= μ(s) • g
November 4, 2012

Physic
ε= ω/t=32.4/0.861=37.63 rad/s² φ=ω²/2ε=32.4²/2•37.63=13.95 rad=799.3°
November 4, 2012

Physics
Centripetal acceleration a=ω²•R=T/m R=T/m•ω² The law of conservation of angular momentum I• ω²=I₀•ω₀² ω=(I₀/I)•ω₀²=(R₀²/R²)•ω₀ R³=(m&#...
November 4, 2012

physics
h = v²/2g Distance= 2h+100(m) The speed is necessary
November 4, 2012

Physics B
F =G•m1•m2/R² the gravitational constant G =6.67•10^-11 N•m²/kg², F1= G•1.5•3.4/1.8² F1= G•1.5•4.5/4.2² F=sqrt(F1²+F2²) α=arctan(F2/F1) The angle with respect to the positive x axis is 180°+ &#...
November 4, 2012

Physics
ma=Fcosα-F(fr) F(fr) =μmg a= (Fcosα- μmg)/m
November 3, 2012

college physics
When the bodies are at rest, the tension in the ropess just equal the weight that is suspended beneath them. The lower body (the stick) has gravity down of m3•g=2•9.8=19.6 N and the tension (T3) in the lower string is T3 = 19.6 N. The rope between the climber and the...
November 3, 2012

physics
ρ(water) =1000 kg/m³ !!!!!!!!!!!!
November 3, 2012

physics
k = 1160 N/m r = 1.22 cm = 0.0122 m x = 0.750 cm =0.0075 m Change in the pressure, when the gauge is taken into water ΔP = F/ A= k•x /π•r² = =1160•0.0075/ π•(0.0122)²= ..... ρ(water) =100 kg/m³ ΔP = ρwater• ...
November 3, 2012

physics
The speeds of the objects after elastic collision are v₁= {-2m₂v₂₀ +(m₁-m₂)v₁₀}/(m₁+m₂) v₂={ 2m₁v₁₀ - (m₂-m₁)v₂₀}/(m₁+m₂)
November 2, 2012

Physics
3.going down and speeding up
November 2, 2012

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•(...
November 2, 2012

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...
November 2, 2012

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
November 2, 2012

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/...
November 2, 2012

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) ...
November 2, 2012

physics
how much force the floor is pressing up on the crate with F(fr)=μN
November 2, 2012

physics
sin θ= n(water)/n(glass) n(glass)= n(water)/ sin θ=1.33/sin60.1=1.53
November 2, 2012

physic
in the wire - 1D (linear waves) in the air -3D(space wave)
November 2, 2012

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
November 2, 2012

physics
.."as shown below" ??????????
November 2, 2012

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
November 2, 2012

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...
November 1, 2012

physics
E=500•24•365•24•3600 = ...(J)
October 31, 2012

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=….
October 31, 2012

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