Sunday
December 4, 2016

# Posts by elena

Total # Posts: 4,386

physics
F= F(fr) + mgsinα= =32.6 +63.8sin59=87.3 N
April 7, 2013

physics
1T=10000 Gauss B=0.02•10⁻⁴= 2•10⁻⁶ T v=8 km/s=8•10³ m/s U=BLv= 2•10⁻⁶•4828• 8•10³=77.25 V
April 7, 2013

Physics
ℰ=-dΦ/dt=-d(NBAcosωt)/dt= =NBAωsinωt = =500•0.05•0.05•20•sin30° =12.5 V
April 6, 2013

Physics (Algebra-based)
PE → KE1 KE1 → Work(fr) +KE2 => PE → Work(fr) +KE2 If the initial height is ‘h₁’, the height of the horizontal section is ‘h₂’, the length of the rough section is ‘s’, then mg (h₁-h₂)=μmgs +mv²...
April 6, 2013

physics
vt=at²/2 t=2v/a=2•19.4/3.2=121.25 s=2.02 min
April 6, 2013

physics
ℰ=-dΦ/dt=-d( BAcosα )/dt cosα=1 ℰ =BA/t= Bab/t=Bb(a/t)=Bbv= =0.125•0.045•4.3=0.024 V
April 6, 2013

physics
ma=F => a=F/m=2/2.5=0.8 m/s² v=v₀-at v=0 t=v₀/a=0.6/0.8=0.75 s.
April 6, 2013

physics
During acceleration (or deceleration) of the bus, she continues to move in previous derection due to inertia, and, therefore, she may fall down.
April 6, 2013

physics
Energy =Power x time =680 W/m2 x 1 second =680 Joule/m2 Energy of 1 photone = hf =hc/λ Number of photones =Energy/energy of 1 photon = N=680• λ/hc=680•478•10⁻⁹/6.63•10⁻³⁴•3•10⁸=…
April 6, 2013

Physics
(a) Torque is M=p⒨•B•sinα p⒨=NIA If M(max) =sin α=1 M(max)=NIAB, I= M(max)/NAB = =40/250•0.12•0.04•1=33.3 A (b) ℰ=-dΦ=-d(NBAsinωt)/dt= =-NBAωcosωt ℰ(max)=NBAω=2πNBAf= =2π•250&#...
April 6, 2013

physics
(a) I =cε₀E²/2 =3•10⁸•8.85•10⁻¹²•(7.9•10⁻⁶)²/2=8.2•10⁻¹⁴W/m² (b) P=I•A=I•πD²/4=8.2•10⁻¹⁴•π•2.1²/4=2.84•...
April 5, 2013

physics
PE=mgh=10•2=20 J. PE->KE
April 5, 2013

physics
Question????
April 4, 2013

Physics
The speed at the 5-m level is of the same magnitude on the way up and on the way down=> s=(v²-v₀²)/2g Solve for v₀
April 4, 2013

Physics 2
tanα=x/L=3.2•10⁻³/9=3.56•10⁻⁴ tanα≈sinα bsinα=kλ b= kλ/sinα=1•530•10⁻⁹/3.56•10⁻⁴=1.5•10⁻³ m
April 2, 2013

Physics
M=Iε ε=M/I = 22.9/0.168 = 136.3 rad/s² 2πN=2πn₀t + εt²/2 2πn=2πn₀ + εt n₀=0 => 2πN= εt²/2 2πn= εt => t=2πn/ε N= πn²/ε n=sqrt {εN/π}= =sqrt{136....
April 2, 2013

physics
Δp(rocket)=Δp(gas)= mv=26•182=4732 kg•m/s
April 2, 2013

Physics
2s=ct s=ct/2=3•10⁸•2.56/2=3.84•10⁸ m
April 2, 2013

Physics
2s=vt s=vt/2=345•4.4/2=759 m
April 2, 2013

Physics
t=2s/v=2•150/345=0.87 s
April 2, 2013

Physics
Speed of sound at 20⁰ v=343.1 m/s λ=v/f=343.1/512 =0.67 m
April 2, 2013

Physics
M=M(fr) M=p⒨Bsinα sinα=sin90=1, M=NIAB M(fr)=F(fr)R=μF⒩R NIAB =μF⒩R F⒩= NIAB/μR= =425•0.27•3•10⁻³•0.21/0.81•0.011= =8.11 N
April 2, 2013

Physics
λ=v/f Speed of sound at 20⁰ v=343.1 m/s f=v/ λ=343.1/0.667=517.4 Hz
April 2, 2013

machanics
A vertical distance covered for t₁=10 s of accelerated motion is h₁=at₁²/2. The speed at this height is v₁=at₁. The distance covered at decelerated motion during t₂=15- t₁=15-10=5 s is h₂=v₁t₂-gt₂²/2. ...
April 2, 2013

physics
h=at²/2 a=2h/t²=2•0.76/5.2²=0.056 m/s² Two equations for the loads -m₁a=m₁g-T₁ => T₁=m₁(g+a) ….(1) m₂a=m₂g-T₂,=> T₂=m₂ (g+a) ….(2) and the 3rd equation (on the base of Newton&#...
April 2, 2013

physics
See the Related Questions below.
April 2, 2013

physics...
v=sqrt(v₁²+v₂²) = sqrt(4+1) =2.236 m/s s=vt=2.236•5=11.18 m
April 2, 2013

PHYSIcs!!!
h=gt²/2=> t=sqrt(2h/g). s=vt=> v=s/t=s/ sqrt(2h/g)= =20/sqrt(2•2/9.8)=31.3 m/s
April 2, 2013

simple PHYISCS
h=gt²/2 t=sqrt(2•5/g)=1.01 s
April 2, 2013

physics
N= mgcosα F(fr)=μN (a) T₁= mgsinα -F(fr) = = mgsinα - μ(s)mgcosα (b) T₂=F(fr) +mgsinα= =μ(s)mgcosα +mgsinα (c) T₃=F(fr) +mgsinα= =μ(k)mgcosα +mgsinα
April 2, 2013

Physics
R₂= 116 Ω, ℰ=120 V, P₁=20.7 W, The resistance of light buble R₁=? R=R₁+R₂, I=V/R, R₁=P₁/I²=P₁R²/V²=P₁(R₁+R₂)²/V². R₁²+(2R₂ - V²/P₁)R₁+R₂...
April 1, 2013

Physics
80•110•10⁶•5.9 =5.192•10¹⁰ W=5.192•10⁷ kWh, 5.192•10⁷•0.11=5.71•10⁶ dollars
April 1, 2013

Physics
ℰ=IR=IρL/A => I₁ρL₁A = I₂ρL₂A L₂=I₁L₁/I₂=2.3•52/2.9=41.2 m
April 1, 2013

Physics
R=4.9•10⁹ Ω V=68•10⁻³V I=V/R=68•10⁻³/4.9•10⁹=1.39•10⁻¹¹ A I=q/t =Ne/t N=It/e=1.39•10⁻¹¹•0.45/1.6•10⁻¹⁹=3.9•10⁷
April 1, 2013

Physics
April 1, 2013

Physics
M=F(fr)•(d/2) =μ•F•(d/2)= 0.15•0.62•1.2•10⁻²/2 =0.000558 N•m
April 1, 2013

Physics
(a)KE=mv²/2 (b) PE=mgh (c) KE1=KE+PE (d) mv₁²/2= mv²/2+mgh v₁= sqrt(v² +2gh)
April 1, 2013

CHM 1010
p₁V₁=p₂V₂ p₂=p₁V₁/V₂
April 1, 2013

Physics-friction problem
ma=F(fr) =μN=μmg a= μg. s=(v₀²-v²)/2a= =(v₀²-v²)/2μg => v=sqrt{v₀²-2μgs}= =sqrt{21.2²-2•0.005•9.8•58.5} = =21.06 m/s. For the 2nd case: s=(v₀²-v²)/2μ₁g= =(21.2...
April 1, 2013

physics
h=v₀t+gt²/2, gt²+2v₀t-2h=0 Solve for t. v= v₀+gt
April 1, 2013

Physics - Electric Potential
ΔPE= -Work=-qΔφ= -{(-0.15)•(13-60)} = =-7.05 J
April 1, 2013

Physics
F=ILBsinα B=F/ILsinα=0.15/67•45•sin51.5⁰=6.35•10⁻⁵ T
April 1, 2013

PHYSICS
Work =500mgh=500•12•9.8•2=117600 J. You need 117600•100/20 =588000 J 1 kg gives 30•10⁶J, mass of burning fat is 588000/30•10⁶ = 0.0196 kg
April 1, 2013

Physics
h=at²/2=20•16/2=160 m
April 1, 2013

Physics
(a) (m₁+m₂)v=m₁v₁+m₂v₂ v₁(a)= {(m₁+m₂)v-m₂v₂}/m₁ (b) (m₁+m₂)v=m₁v₁-m₂v₂ v₁(b)= {(m₁+m₂)v+m₂v₂}/m₁ (c) (m₁+m₂)v=m₁v...
April 1, 2013

physics
L=2mvx=2•m•v•(b/2)=2•3•5.41•3.15/2= ...
April 1, 2013

physics
m₁=m= 70 kg m₃=0.175 kg, v₃=10 m/s Let v₃ be positive and directed to the right 0= - m₁v₁+m₃v₃ v₁=m₃v₃/m₁=0.175•10/70=0.025 m/s (directed to the left) m₃v₃ =(m₂+m₃)v v= m₃...
April 1, 2013

physics
Q1=Q2+cm•Δt c=(Q1-Q2)/ m•Δt= =(12000-1300)/0.185•(73-22)= =1134 J/kg•℃
April 1, 2013

Physics
F=qvB sin12⁰ 1.8F=qvBsinφ sinφ/sin12⁰ =1.8 sinφ =sin12⁰•1.8=0.208•1.8=0.374 φ=sin⁻¹0.374=22⁰
April 1, 2013

Q(gained) =Q(lost) Q(lost) =Q₁+Q₂+Q₃ Q₁ = c₁m(Δt₁)=2020•1•(120-100) = 40400 J Q₂ = Lm=2256000•1= 2256000 J Q₃=c₂m(Δt₂)=4186•1•(100-85) = 62790 J Q(lost) =40400 +2256000+62790 =...
March 31, 2013

Q(gained) =Q(lost) Q(gained) =Q₁+Q₂+Q₃ Q₁ = c₁m(Δt₁)=2020•1•(120-100) = 40400 J Q₂ = Lm=2256000•1= 2256000 J Q₃=c₂m(Δt₂)=4186•1•(100-85) = 62790 J Q(gained) =40400 +2256000+62790 =...
March 31, 2013

physics
After the 1st rebounce the speed is v/2, after the 2nd rebounce – v/4, after the third rebounce –v/8, => m(v/8)²/2=mgh₁ v=sqrt(128gh₁) =141.7 m/s mv²/2=mgh h= v²/2g=141.7²/2•9.8=1024 m
March 31, 2013

math
An elementary school collected a total of 240 cans during a food drive. Grade 3 students collected 1/3 of all the cans grade 4 students collected 52 cans, and the rest of the cans were collected by grade 5 students. How many cans did grade 5 collect? A.28 B.80 C.108 D.188
March 29, 2013

physics
Assume g=10 m/s². The ball upward motion 0=v₀-gt, t=v₀/g=10/10=1 s. The train motion for time 1 s 0= v-at, a=v/t=5/1 = 5 m/s², the distance s= v t -at²/2 =5•1 -5•1²/2 = 2.5 m
March 29, 2013

Physics. LAST PROBLEM!!
A small metal ball with a mass of m = 82.5 g is attached to a string of length l = 1.72 m. It is held at an angle of θ = 58.5° with respect to the vertical. The ball is then released. When the rope is vertical, the ball collides head-on and perfectly elastically with ...
March 26, 2013

physics
y=gt²/2 t=sqrt(2y/g) =sqrt(2•920/9.8)=13.7 s
March 26, 2013

Physics
mv²/2=qU v=sqrt(2qU/m) R=mv/qB= (m/qB)• sqrt(2qU/m)= R3/R4 = sqrt{ 2Um q₄B²/q₃B²2Um)= =sqrt(q₄/q₃) sqrt(4e/3e)=1.15
March 26, 2013

Physics
T=t/N=11.8/10=1.18 s ω=2π/T=2π/1.18=5.32 rad/s T=mv²/R=mω²R=0.013•5.32 ²•0.93=0.34 N
March 25, 2013

physics
s=2.08 m m=0.592 kg R=0.0786 m a is the acceleration of the system (m1+m2) m₁a= T₁ m₂a= m₂g-T₂ Iε=M => mR²•a/2R = (T₂-T₁)R, T₂-T₁= ma/2, a= m₂g/( m₁+m₂+m/2)=... a=v²/2s v=sqrt(2as...
March 24, 2013

physics
s=2.08 m m=0.592 kg R=0.0786 m a is the acceleration of the system (m1+m2)
March 24, 2013

physics
m₁a= T₁ m₂a= m₂g-T₂ Iε=M => mR²•a/2R = (T₂-T₁)R, T₂-T₁= ma/2, a= m₂g/( m₁+m₂+m/2)=... a=v²/2s v=sqrt(2as)=... ω=v/R=...
March 24, 2013

Physics
Magnetic field of the current-carring wire at distance b from it is B=1/2πb If B=B(Earth)/3= 5•10⁻⁵/3 T, I=2πbB= 2π•0.3•5•10⁻⁵/3 = …
March 24, 2013

Physics
x=0.45 m, D=0.12 m, I= 2 A, B=2.1 kG=2100G= 0.21 T μ₀=4π•10⁻⁷ H/m B=μ₀nI = μ₀NI/x N=Bx/ μ₀I The length of the wire L=N•πD= Bx πD / μ₀I= =0.21•0.45•π•0.12/4π&#...
March 24, 2013

Physics
r1=r2=3 m
March 24, 2013

Physics
The speed is v=s/t=186/3=62 km/h <65 km/h He can arrive on time.
March 24, 2013

Physics
1. g =GM/R² g₁=GM/(R+h)² g₁/g=30/100= GM R²/(R+h)²GM => 0.3= R²/(R+h)² Solve for “h” (Earth’s radius is R = 6.378•10⁶ m) 2. mv²/(R+h)= GmM/(R+h)² v=sqrt { GM/(R+h)}
March 24, 2013

physics
Tsinα =ma Tcosα =mg tanα=a/g=3.2/9.8 = 0.33 α = 18°
March 24, 2013

Physics
E =kq/r² (a) E(x) = E₁-E₃=kq₁/r² - kq₃/r² = =9•10⁹{(1•10⁻⁶/0.23²)- (7•10⁻⁶/0.23²)}= -1.02•10⁶ V/m (b) An altitude of a triangle is h=0.46cos30=0.46•0.866=0.398 m E(y...
March 24, 2013

physics
1. Flowrate=A•v=21•0.89 = 18.69 m³/s 2. A₁v₁=A₂v₂ v₂=A₁v₁/A₂=21•0.89/17=1.1 m/s
March 22, 2013

Math/Physics
Q=55034175 J c(ice)=2060 J/kg•℃ λ=330000 J/kg c(water)=4183 J/kg•℃ Q=Q₁+Q₂+Q₃ Q=c(ice)m(12.15-0)+λm+c(water)m(t-0), Q/m=12.15•c(ice) +λ+c(water)•t. Solve for “t”
March 22, 2013

physics
R=ρL/A R =4ρL/πd² R₁ =4ρL/ (π4d²- πd²) =4ρL/ 3πd² R₁=R/3
March 21, 2013

Physics
sinα=R/L=0.3/1=0.3 α=17.45° mv²/R=Tsinα …..(1) mg=Tcosα …..(2) Divide (1) by (2) v²/Rg=tanα v=sqrt(R•g•tanα)= =sqrt(0.3•9.8•0.31)=0.27 m/s ω=v/R=0.27/0.3=0.9 rad/s f= ω/2π=0.9/2•3.14=...
March 21, 2013

physics impulse
1) p=mv=2•4= 8 kg•m/s 2) KE=mv²/2 3) At elastic collision p= - mv 4) Δp= p1-(-p2) =mv – (-mv)= 2mv 5) p(wall)= Δp=2mv 6) F•Δt=mv F= mv/ Δt
March 21, 2013

physics
We’ll use Kirchhoff’s Current Law: At any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node. Node: I₁, I₂ and I₁₂ currents: I₁+I₂-I₁...
March 20, 2013

Physics
sini/sinr=n2/n1 n2=n1(sini/sinr)=1.45(sin64.8/sin68.0)=...
March 20, 2013

Ecology
The eﬀect of humans on the environment is more drastic than that of other species because people have a greater ability to 1. adapt to seasonal changes. 2. learn new skills. 3. alter the environment. 4. eat diﬀerent types of food.
March 19, 2013

Biology
Eutrophication refers to 1. the concentration of a toxic substance in the tissues of organisms. 2. depletion of mineral resources as a result of leaching. 3. the warming of the earth’s surface. 4. the damage to the ozone layer that protects the earth from UV light. 5. ...
March 19, 2013

Physics
http://en.wikipedia.org/wiki/Torque
March 19, 2013

Physics
F=Rmv=140•0.0026•510/60=3.1 N
March 19, 2013

Physical Science
convection.
March 18, 2013

phical science
Neutrinos are almost massless, travel close to the speed of light, and pass through matter almost undisturbed. Photons, on the other hand, have no mass, travel at the speed of light, yet are absorbed and/or reflected even by fairly sparse matter such as gasses. A photon has an...
March 18, 2013

physics
kx²/2 = mv²/2 v=sqrt(kx²/m)=sqrt(244•16•10⁻⁴/0.099) =...
March 18, 2013

physics
v₀ = 8.9 m/s m=4.1 kg R = 0.116 m μ=0.34 === F=ma F(fr)=μmg F=F(fr) ma= μmg a= μg=0.34•9.8=3.33 m/s² The torque M=Iε=(2mR²/5)•ε M=F(fr)•R= μmgR (2mR²/5)•ε= μmgR ε= 5μmgR/2mR²...
March 18, 2013

physics
kx²/2=mgh k=2mgh/ x²= 2•0.0961•9.8•0.591/(0.04754)²=...(N/m)
March 18, 2013

Physics
See my answer to a similar question below under related questions.
March 17, 2013

Physics
L₁= μ₀N²A/x₁ => x₁=μ₀N²A/L₁ L₂= μ₀N²A/x₂ => x₂= μ₀N²A/L₂ Δx=x₂-x₁=μ₀N²A{(1/L₁)–(1/L₂)}
March 17, 2013

Physics
Work=mgh==30•9.8•250 =... Power =mgh/t=30•9.8•250/30•60 =...
March 16, 2013

physics
a(centr)= mv²/R=0.036•36²/1.31 =…
March 16, 2013

Chemistry
0.25mol of CO are mixed with 0.90mol of H2 and heated to 950 degrees celcius in a 15L flask at equilibrium 0.190mol of H2O were present, what is the concentration of the other reactants and products at equilibrium and what is Kc
March 16, 2013

Physics 1
The law of conservation of linear momentum 0=mv-MV V=mv/M= 12•7.7/76.9 =1.2 m/s S=Vt=1.2•2•60 = 144.2 m
March 14, 2013

physics
ω=v/R ω =2πf v/R=2πf f=v/2πR= …
March 14, 2013

Physics (Algerbra-based)
a(centr) = a•cosα=14.3•cos30=… a(tang)=a•sinα=14.3•sin30=… a(centr)= v²/R, v=sqrt{a(centr) •R}=...
March 14, 2013

physics
The airplanes have the same speed -true The airplanes have the same velocity-false
March 14, 2013

Physics
March 14, 2013

physics
C=Q/V C=εε₀A/d Situation I: The capacitor is disconnected from the battery, => Q=const (a) V=Q/C=Qd/εε₀A d₁=4d=> V₁=Q/C₁=Qd₁/εε₀A=4 Qd/εε₀A=4V (b) U=CU²/2=Q²d/2εε...
March 14, 2013

PHYSICS
ΔKE=ΔPE=mgΔh=60•9.8•42 =24696 J
March 14, 2013

(a) cm₁(80-T)=cm₂(T-27) 2(80-T)=20(T-27) T=31.8 ℃ (b) λ= 330000 J/kg Q= λm=330000•0.1 =33000 J
March 14, 2013

Physics
Motion of the particle without deflection => F(el) = F mag) qE =qvB B=E/v=2607/6.81•10³=0.38 T For the second particle F=qE-qv₁B v₁=(F+qE)/qB= =1.8•10⁻⁹•3.72•10⁻¹²•2607}/ 3.72•10⁻¹²&#...
March 13, 2013

Physics
mv²/R=qvB R=mv/qB ΔR=R₂-R₁= =m₂v/qB - m₁v/qB= = v(m₂ - m₁)/qB)= =3•10⁵•(238-235)•1.67•10⁻²⁷/92•1.6•10⁻¹⁹•0.6= =1.7•10⁻⁴ m
March 13, 2013

Physics
ΔV=VB-VA =kq/r(B)-kq/r(A)= =kq{r(a)-r(B)}/r(A)•r(B). q = r(A)•r(B)•ΔV/k{r(a)-r(B)}= =(3.4-4.5)•45/9•10⁹•3.4•4.5 = = - 9.5•10⁻¹⁰ C
March 12, 2013