Wednesday
July 30, 2014

Posts by Elena


Total # Posts: 4,343

science
p=mg/A = 50•9.8/2(0.15•0.005)= =326666 Pa

Physics
x: Fcosα-μN =0, y: mg-N-Fsinα=0 =>N= mg-Fsinα, μ= Fcosα/N = Fcosα/(mg-Fsinα)= =77•cos30/(24.5•9.8-77•sin30)= =0.33

physics
h=gt²/2 = 10•2²/2=20 m v=gt =10•2 =20 m/s v=v₀-gt₁ v=0 t₁= v₀/g=15/10=1.5 s h₁=v₀t₁-gt₁²/2 = =15•1.5 -10•1.5²/2=11.25 m a=Δv/Δt= (-15-20)/0.02= - 1750 m/s

physics
1 amu = 1.6605•10⁻²⁷ kg 19.992439 amu = 3.3197•10⁻²⁶ kg m=10 m(p) +10 m(n) = =10• (1.6726+1.6749) •10⁻²⁷ = =3.3475•10⁻²⁶ kg Δm=(3.3475-3.3197) •10⁻²⁶= =0.027...

Physics
s₁=45 m α=26⁰ s₂=? ΔPE +W(fr)₁ =KE =W(fr)₂, ΔPE +W(fr)₁ =W(fr)₂, mgh+ F(fr)₁•s₁ = F(fr)₂•s₂. h=s₁•sinα, F(fr)₁ =μ•N₁=μ•mgcosα, F(fr)&...

AP Physics
mg=mv²/r v=sqrt(rg)

Physics
a=ω²R =(2πn)²R= (2•3.14•60)²•0.15 = …

Physics
a. sandpaper

physics
L=vₒ²•sin2α/g= vₒ²•2sinα•cosα/g h= vₒ²•sin²α/2g, L/h= 2•vₒ²•2sinα•cosα•g/ vₒ²•sin²α• g= =4/tanα tanα = 4h/L = 4•...

physics
v₁=v₀-gt₁ v₀=v₁+ gt₁=18+9.8•5.4= 40.54 m/s At the top point v=0 0 =v₀-gt t = v₀/g=40.54/9.8 =4.14 s. t₃=t₂- t=5.4 – 4.14 = 1.26 s v₂=gt₃ = 9.8•1.26 = 12.38 m/s (directed dowmward)

Physics
A(x) =45.6•cos51.2 = 28.57 A(y) = 45.6•sin51.2 =35.74 B(x)= -23.6•cos32.8 = -19.84 B(y) = 23.6•sin32.8=12.78 C(x) = 0 C(y) = -34 (A-B+C)(x)= 28.57-(-19.84) +0 =47.84 (A-B+C)(y) = 35.74-12.78 +(-34)=-11.04 (A-B+C) =sqrt[47.84²+(-11.04)²] = 49.1 tan...

college physics
Example 2.2: Electric Field on the Axis of a Rod (page 2-17) http://web.mit.edu/viz/EM/visualizations/coursenotes/modules/guide02.pdf

college physics
F=k•q₁•q₂/r² k =9•10⁹ N•m²/C² e =1.6•10⁻¹⁹ C. F=k•e²/r²= =9•10⁹•(1.6•10⁻¹⁹)²/(0.542•10⁻¹⁰)² = =7.84•10⁻...

physics
N= 0.1 rev n= 4.31•10² rev/s t=N/n = 0.1/4.31•10² = 2.32 •10⁻⁴ s v=s/t =60000/2.32•10⁻⁴=2.59•10⁸ m/s Ans. d

physics
h =s/2 = vt/2= 1530•8/2 =6120 m

Pysics
t₁=s₁/v₁ =185/6=30.83 s t₂=s₂/v₂= 310/2=155 s v(ave) =(s₁+s₂)/(t₁+t₂)= =(185+310)/(30.83+155)=2.66 m/s

physics
s=at²/2 a=2s/t² F=ma eU =Fs =mas =m2s²/t² U= 2ms²/et² = =2•9.1•10⁻³¹•(0.15)²/1.6•10⁻¹⁹•(19•10⁻⁹)²= =709 V

physics
http://www.physicsforums.com/showthread.php?t=200266

PHYSICS!!!
a=ω²R =(2π/T)²R =4g T= πsqrt(R/g)= 3.7 s

college physics
http://www.physics.drexel.edu/~wking/courses/phys102_s08/notes/rec1_sols.pdf

physics
v= v₀ + at v₀=0 a=v/t=21500/3600•6.9 =0.87 m/s² s= at²/2 = 0.87•6.9²/2=20.6 m

physics
mgh₁ = mv₁²/2 v₁=sqrt(2gh₁) = sqrt(2•9.8•4.31)=9.2 m/s mv₂²/2= mgh₂ v₂ =sqrt(2gh₂) = sqrt(2•9.8•2.51)=7 m/s a=[v(fin) – v(in)]/t v(fin) =v₂ (directed upward ) v(in)] = v₁ (directed d...

Physics
v₀=7m/s; d=4 m; L 45 m; a= 0.5 m/s². (v₀t + at²/2) - (v₀t) = d t =sqrt (2d/a) = sqrt(2•4/0.5) = 2.83 s (a) t=2.83 s v₁=v₀+at = 7 + 0.5•2.83 = 8.42 m/s x = v₀t+ at²/2 = 7•2.83 + 0.5•2.83²= 21.8 m (b) s ...

physics
(a) Upward motion v=v₀ -gt v=0 v₀ =gt =9.8•1.9 =18.62 m/s (b) h=v₀t -gt²/2 = 18.62•1.9 - 9.8•1.9²/2= =35.38 – 17.69 = 17.69 m (c) If H is the height of the building t₀= 9 – 1.9 = 7.1 s H+h = gt₀²/2 = 9.8...

physics
h= gt²/2 t=sqrt(2h/g) = sqrt(2•196/9.8)=6.32 s. The first 96 m h/2=gt₁²/2 t₁=sqrt(h/g)=sqrt(196/9.8)=4.47 s. The 2nd 96 m t₂=t-t₁=6.32-4.47 =1.85 s

Physics
h=v₀t +gt²/2 v= v₀+gt v₀ =v-gt h=( v-gt)t + gt²/2 = =vt - gt² + gt²/2= = vt - gt²/2. gt² -2vt +2h = 0 t = (2•34.9±sqrt{(2•34.9)²-4•9.8•2•34.9}/2•9.8 = 0.7 s v₀ =v-gt =34.9 – 9....

physics
n=30 rpm = 30/60 =0.5 rev/s ω=2πn =2π•0.5 = π =3.14 rad/s (along the axis of rotation)

physics
See the answer in Related Questions

phyiscs
H=gt²/2 t =sqrt(2H/g) = sqrt(2•81/9.8)=4.07 s h=(1-0.28)H =58.32 s t₁ =sqrt(2h/g) =3.45 s. t₂=4.07 – 3.45 = 0.62 s. v₁=gt₁ =9.8•3.45 =33.81 m/s v₂ = gt₂ =9.8•4.07 = 39.89 m/s

Physics
F =G•m₁•m₂/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², F₁=F₂ = G•m₁•m₂/R²= =6.67•10⁻¹¹•1•100/1²=6.67•10⁻ ⁹ N.

physics
T₁=2πsqrt(m₁/k) T₂ =2πsqrt(m₂/k) T₂ /T₁ =sqrt{ m₂/m₁} T₂ = T₁sqrt{ m₂/m₁}= =3.5•sqrt(2/1) =4.95 s.

Phyics
v₂t +at²/2 -v₁t =10.7 0.6t²-2.6t -10.7 =0 t=6.92 s

physics
1. F(el) =F(magn) qE=qvB v=E/B=1.08•10⁴/2•10⁻³ =5.4•10⁶ m/s ma=mv²/R= qvB q/m=v/RB =5.4•10⁶/1.53•10⁻²•2•10⁻³ = =1.76•10¹¹ C/kg +> This is electron (e/m= 1.6•10S...

physics
Centripetal acceleration a=ω²•R =(2πn)²•R =4π²n²•R => n=sqrt{aR/4π²} =sqrt{1090•9.8•0.123/4•π²}=5.77 rev/s

physics
v=v₀+at a= (v-v₀)/t

physics
(a) E=0 (b) E=k•2λ/r =9•10⁹•2•36•10⁻⁹/0.135=4800 N/C (c) E=k•2λ/r =9•10⁹•2•36•10⁻⁹/1.25=518.4 N/C

Physical Science
Two magnets will be attacted by their opposite poles, and each will repel the like pole of the other magnet. A. attract each other.

science
Osmosis http://en.wikipedia.org/wiki/Osmosis http://www.beaconlearningcenter.com/documents/1965_3263.pdf

physics
pressure = Weight/area = mg/A = = 50000 x 9.8/5 = 98000 Pa

physics
ma=-mg +F a= F/m- g = 1005/92.3 - 9.8 = =10.9 -9.8 = 1.1 m/s²

Physic,
From http://teacher.nsrl.rochester.edu/phy_labs/appendixe/appendixe.html Error in experiments have several sources. First, there is error intrinsic to instruments of measurement. Because this type of error has equal probability of producing a measurement higher or lower numeri...

physics
P=Fv v=P/F

Physics
mv=(m+M)u u=mv/(m+M)

Physics (Kinematics)
s= at²/2

Physics (Kinematics)
s=at²/2 a=2s/t² = …

Physics (Kinematics)
v=v₀+at a=(v-v₀)/t = … s= v₀t + at²/2=...

phys
c. a spinal reflex

physics
ma=mgsinα a=gsinα

physics
F=mgsinα=Wsinα =200 x 0.5 =100 N

physics
m=W/g For upward motion ma= T- mg a=( T- mg)/m=(T-W)/m For downward motion ma=mg-T a = (mg-T)/m=(W-T)/m

AP Physics B
a. PE = mgh=1.5•9.8•0.5 = 7.35 J b. KE=PE = 7.35 J c. KE = mv²/2 v= sqrt(2•KE/m) = =sqrt(2•7.35/1.5)=3.13 m/s mv + 0 = 2mu u=mv/2m = v/2= 3.13/2 =1.565 m/s d. KE₂=2m•u²/2 = 2•1.5•1.565²/2 =3.68 J e. KE₂ = W(fr)=F(fr...

physics
v₀ = 0 v = ω R ω=v/R =15/0.3=50 rad/s ω =εt=> ε = ω/t= 50/8 =6.25 rad/s² 2πN = εt²/2 N= εt²/4π=6.25•8²/4π= 31.8 rev

physics
ω= ω₀- εt 2πn=2πn₀ - εt ε=2π(n₀-n)/t =2π(30-20)/2=31.4 rad/s² N= εt²/4π = 31.4•2²/4π =10 rev L=2πR•N =2π•0.05•10 =3.14 m

Physics
If the net force on Charge B is zero, => the electric field strength is zero at the point B (charge B location). vector E(A) +vector E(C) +vector E(D) = 0 => At the point B: Vectors E(A) and E(C) are direcred to the right => vector E(D) has to be directed to the left ...

physics
If the net force on Charge B is zero the electric field strength is zero at this point. vector E(A) +vector E(C) +vector E(D) = 0 => At point B: Vectors E(A) and E(C) are direcred to the right => vector E(D) has to be directed to the left => charge D is positive. kq(A...

science
h=gt^2/2

Physics
ma=Fcosα –F(fr) a=0 0=Fcosα – μN= Fcosα – μmg (b) F = μmg/cosα = (c) W= Fcosα•d = (d) W(fr) = μmg•d =

Physics
mass of the bullet is m = 25 kg (???) mv²/2 =F(res)•d F(res) = mv²/2d d₁= mv₁²/2•F(res)

Physical Science
1) t=s/v= 28/4 = 7 hr 2) KE=PE=mgh =7.2 •9.8•1.2 = …J 3) Q=mcΔT ΔT= Q/mc = 30000/0.39•3.9 = …

Physics
N₁=N₀exp(-λt₁) N₁/N₀ = exp(-λt₁) ln(N₀/N₁) =λt₁ λ = ln(N₀/N₁)/t₁= =ln(2/1.6)/156=0.223/156 (day⁻¹) N₂=N₀exp(-λt₂) = =2•exp(-0.223•201/156)=2&...

Physics
angular distance = 880+340 =1220 degr angular displacement =880-340 =540 degr

Physics Angular Motion
ma=T-mg mv²/R=T - mg T = mv²/R + mg

Physics Angular Motion
a= v²/R v=sqrt(aR)

physical sciences
water H₂O acetone CH₃-C(O)-CH₃ ethanol CH₃-CH₂-OH or C₂H₅OH methylated spirit CH₃ OH http://en.wikipedia.org/wiki/Water http://en.wikipedia.org/wiki/Acetone http://en.wikipedia.org/wiki/Ethanol http://en.wikipedia.org/wiki/Methanol

Physics
Upward motion of the weight h =v₀t-gt²/2 v= v₀ -gt v=0 => v₀ =gt => t = v₀ /g =9/9.8 =0.92 s h = v₀²/2g =9²/2•9.8 =4.13 m Let h₀ is the height of helicopter when the weight began its motion. Then for downward motion...

physics
h=gt²/2 t=sqrt(2h/g) v(y) = gt v(x) =15 m/s v= sqrt{v(x)²+v(y)²}

physics
L=10 log₁₀ (I/I₀) I₀= 10⁻¹² W/m² I/I₀ = 10^(L/10) I= I₀•10^(L/10) = =10⁻¹²•10^(130/10)=10 W/m² I₁ = I/19=10/19= 0.53 W/m² L=10 log₁₀ (I₁/I₀) = =10 log...

physics
L=10 log₁₀ (I/I₀) I₀= 10⁻¹² W/m² I/I₀ = 10^(L/10)= =10^(L/10)= I= I₀•10^(L/10) = =10⁻¹²•10^(95/10) =3.16•10⁻³W/m² E= I•A•t=I•πr²•t= =3.16•...

physics
Centripetal (centrifugal ) acceleration a= 2 m/s² a=v²/R v=sqrt(aR) =sqrt(2•200) =20 m/s Centripetal force is F=ma= 2500•2 = 5000 N http://www.engineeringtoolbox.com/centripetal-acceleration-d_1285.html

physics
ΔL= L₁ - L₂ = =10 log₁₀(I₁/I₀) – 10log₁₀(I₂/I₀) = =10 log₁₀(I₁/I₂) ΔL/10 = log₁₀(I₁/I₂) I∼A² A₁/A₂=sqrt{ I₁/I }=sqrt{10^( ...

physics
(a) L=10 log₁₀ (I₁/I₀) ΔL= L₁ - L₂ = =10 log₁₀(I₁/I₀) – 10log₁₀(I₂/I₀) = =10 log₁₀(I₁/I₂) ΔL/10 = log₁₀(I₁/I₂) I₁/I₂ =...

physics
(a) v=331.3 + 0.606•t =331.3 + 0.606•22 =344.6 m/s s=vt=344.6•0.8=275.7 m

physics
PE=KE mgh=mv^2/2 v=sqrt(2gh) KE= mv^2/2

physics
ΔL= αLΔtº Δtº = ΔL/αL= =0.1/11.8•10⁻⁶•1000=8.43º tº=0+8 =8℃

Physics
x₁=x₂=x F=F₁+F₂ F/x= F₁/x +F₂/x = F₁/x₁+F₂/x₂ => k=k₁+k₂= 35+55 = 90 N/m

solid mechanics
External diameter D=38 mm Inner diameter d=38 -2•2.5 = 33 mm E=2.05•10⁵ N/mm² A=π(38²-33²)/4 =278.8 mm² I = π(38⁴-33⁴)/64 = 44140 mm⁴ L=2300 mm P(cr) = π²•E•I/L² = = π²2.05•...

Biomechanics
h=v²/2g v=sqrt(2gh)=...

physics
T=2πsqrt(L/g) => L=T²g/4π²= =2.15²•9.8/4•π²=1.1475 m L₁=L+ΔL = L+αLΔt= =1.1475 + 19•10⁻⁶•1.1475•133 =1.1504 m T₁=2 πsqrt(L₁/g) = = 2 πsqrt(1.1504/9.8)=2.1527 s...

physics
ΔL=L₁-L = L+ΔL -L = αLΔt L= ΔL/ αΔt =0.195 m /12•10⁻⁶•50 =325 m

physics
λ=3.35•10⁵ J/kg r=2.26•10⁶J/kg Q₁=Q₂ λm₁=rm₂ m₁=rm₂/λ= 2.26•10⁶•2.32/3.35•10⁵=15.65 kg

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= 405•2.9/4.8 = 244.7(N) Torques about the point D F(S) •BD - mg•CD = 0 F(S)= mg•CD/BD = 405•1.9...

physics
(a) 0.12•I•A = P, A=P/0.12•I = 150/0.12•700 = 1.79 m². (b) 2•365.25•(9•0.150)kW•h• 3 ¢/kW•h = =2958.5 ¢

physics
λ=v/f =s/t•f=85000/12•11.5 =.... (m)

physics
λ=v/f f=v/ λ =5.25/43 =0.122 s⁻¹=7.23 min⁻¹

Physics
A: p₁=3 atm =3.04•10⁵ Pa, V₁=1 L = 10⁻³ m³; B: p₂=6 atm = 6.08•10⁵ Pa, V₂ =5L=5•10⁻³m³; C: p₃= 4.5 atm = 4.56•10⁵ Pa, V₃=11L = 11•10⁻³m³. A->B: W&#...

physical
0=mgsinα - F(fr)= =mgsinα - μN= =mgsinα - μmgcosα. μ=sinα/cosα =tanα α =tan⁻¹0.58 =30.11º

Physics
p₁/T₁=p₂/T₂ T₁=273+20 =293 K, T₂=273+58=331 K p₂=p₁T₂/T₁= ...

physics
v(x) =v₀(x) =v₀cosα =const

physics
Q=Q₁+Q₂+Q₃= =mc(ice)(27-0)+mλ(ice) +mc(water) (35-0)= =5(2060•27 + 335000 + 4183•35) = …

physics
L=L₁+L₂=L₀₁+ΔL₁ +L₀₂ + ΔL ₂= = L₀₁+α₁•L₀₁•ΔT +L₀₂ + α₂•L₀₂•ΔT= =1+ 23.1•10⁻⁶(450-25) +1+ 12•10...

physics
T=F(buoyancy) –mg = = ρ(water)Vg - ρ(balsa)Vg= =Vg[ρ(water) - ρ(balsa)] = =0.25³•9.8(1000 – 160)=129 N

physics
p=p₀+ρgh= 1.013•10⁵ + 800•9.8•18 = =2.42•10⁵ Pa

physics
p= F₁/A₁= F₂/A₂ F₁/π R₁²= F₂/π R₂² F₁ = F₂ R₁²/R₂²= m₂g •R₁²/R₂²= =1500•9.8 •0.005²/0.5²=1.47 N

physics
Standard reference sound intensity I₀= 10⁻¹² W/m² I₁=10⁷W/m² L=10 log₁₀ (I₁/I₀) = =10 log₁₀(10⁷/10⁻¹²) = =190 dB

physics
N=L/λ =Lf/v =10•215/130=16.5 => 16

physics
f=f₀/{1 – (v/u)}=960/{1- (34/343)} = =1065 Hz

physics
T=2πsqrt(L/g), g=4π²L/T²=4π²•0.171/0.833² =...

physics
7.7•x = 53• 1 x=53/7.7 =6.88 m

physics
N=(n₂²-n₁²)/2a=(186²-226²)/(-2•6.4)= =1287.5 rev

physics
m₁v₁ - m₂v₂ =(m₁+m₂)u u= (m₁v₁ - m₂v₂)/(m₁+m₂)= =(1.8•10³•15-9•10²•15)/(1.8•10³+9•10²)= =13500/2700=5 m/s (eastbound)

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