Wednesday
September 17, 2014

Posts by elena


Total # Posts: 4,331

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
September 26, 2013

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
September 26, 2013

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....
September 23, 2013

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...
September 23, 2013

AP Physics
mg=mv²/r v=sqrt(rg)
September 23, 2013

Physics
a=ω²R =(2πn)²R= (2•3.14•60)²•0.15 = …
September 23, 2013

Physics
a. sandpaper
September 22, 2013

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•...
September 22, 2013

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)
September 21, 2013

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...
September 21, 2013

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
September 21, 2013

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⁻&#...
September 21, 2013

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
September 20, 2013

physics
h =s/2 = vt/2= 1530•8/2 =6120 m
September 20, 2013

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
September 14, 2013

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
September 14, 2013

physics
http://www.physicsforums.com/showthread.php?t=200266
September 14, 2013

PHYSICS!!!
a=ω²R =(2π/T)²R =4g T= πsqrt(R/g)= 3.7 s
September 14, 2013

college physics
http://www.physics.drexel.edu/~wking/courses/phys102_s08/notes/rec1_sols.pdf
September 13, 2013

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
September 12, 2013

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 ...
September 12, 2013

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...
September 12, 2013

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&#...
September 12, 2013

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
September 12, 2013

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....
September 12, 2013

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)
September 12, 2013

physics
See the answer in Related Questions
September 12, 2013

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
September 12, 2013

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.
September 12, 2013

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.
September 12, 2013

Phyics
v₂t +at²/2 -v₁t =10.7 0.6t²-2.6t -10.7 =0 t=6.92 s
September 12, 2013

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•10&#...
September 9, 2013

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
September 9, 2013

physics
v=v₀+at a= (v-v₀)/t
September 9, 2013

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
September 9, 2013

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.
September 3, 2013

science
Osmosis http://en.wikipedia.org/wiki/Osmosis http://www.beaconlearningcenter.com/documents/1965_3263.pdf
August 21, 2013

physics
pressure = Weight/area = mg/A = = 50000 x 9.8/5 = 98000 Pa
August 21, 2013

physics
ma=-mg +F a= F/m- g = 1005/92.3 - 9.8 = =10.9 -9.8 = 1.1 m/s²
August 21, 2013

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 ...
August 20, 2013

physics
P=Fv v=P/F
August 15, 2013

Physics
mv=(m+M)u u=mv/(m+M)
August 14, 2013

Physics (Kinematics)
s= at²/2
August 13, 2013

Physics (Kinematics)
s=at²/2 a=2s/t² = …
August 13, 2013

Physics (Kinematics)
v=v₀+at a=(v-v₀)/t = … s= v₀t + at²/2=...
August 13, 2013

phys
c. a spinal reflex
August 13, 2013

physics
ma=mgsinα a=gsinα
August 12, 2013

physics
F=mgsinα=Wsinα =200 x 0.5 =100 N
August 12, 2013

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
August 11, 2013

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...
August 9, 2013

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
August 8, 2013

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
August 8, 2013

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...
August 8, 2013

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...
August 8, 2013

science
h=gt^2/2
August 8, 2013

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 =
August 8, 2013

Physics
mass of the bullet is m = 25 kg (???) mv²/2 =F(res)•d F(res) = mv²/2d d₁= mv₁²/2•F(res)
August 8, 2013

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 = …
August 7, 2013

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...
August 7, 2013

Physics
angular distance = 880+340 =1220 degr angular displacement =880-340 =540 degr
August 6, 2013

Physics Angular Motion
ma=T-mg mv²/R=T - mg T = mv²/R + mg
August 4, 2013

Physics Angular Motion
a= v²/R v=sqrt(aR)
August 4, 2013

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
August 4, 2013

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...
August 4, 2013

physics
h=gt²/2 t=sqrt(2h/g) v(y) = gt v(x) =15 m/s v= sqrt{v(x)²+v(y)²}
August 3, 2013

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&#...
August 2, 2013

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•...
August 2, 2013

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
August 1, 2013

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^( &#...
August 1, 2013

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 =...
August 1, 2013

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
August 1, 2013

physics
PE=KE mgh=mv^2/2 v=sqrt(2gh) KE= mv^2/2
August 1, 2013

physics
ΔL= αLΔtº Δtº = ΔL/αL= =0.1/11.8•10⁻⁶•1000=8.43º tº=0+8 =8℃
August 1, 2013

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
July 31, 2013

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•...
July 31, 2013

Biomechanics
h=v²/2g v=sqrt(2gh)=...
July 31, 2013

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...
July 30, 2013

physics
ΔL=L₁-L = L+ΔL -L = αLΔt L= ΔL/ αΔt =0.195 m /12•10⁻⁶•50 =325 m
July 30, 2013

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
July 30, 2013

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...
July 30, 2013

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 ¢
July 30, 2013

physics
λ=v/f =s/t•f=85000/12•11.5 =.... (m)
July 30, 2013

physics
λ=v/f f=v/ λ =5.25/43 =0.122 s⁻¹=7.23 min⁻¹
July 30, 2013

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&#...
July 30, 2013

physical
0=mgsinα - F(fr)= =mgsinα - μN= =mgsinα - μmgcosα. μ=sinα/cosα =tanα α =tan⁻¹0.58 =30.11º
July 30, 2013

Physics
p₁/T₁=p₂/T₂ T₁=273+20 =293 K, T₂=273+58=331 K p₂=p₁T₂/T₁= ...
July 30, 2013

physics
v(x) =v₀(x) =v₀cosα =const
July 29, 2013

physics
Q=Q₁+Q₂+Q₃= =mc(ice)(27-0)+mλ(ice) +mc(water) (35-0)= =5(2060•27 + 335000 + 4183•35) = …
July 29, 2013

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&#...
July 29, 2013

physics
T=F(buoyancy) –mg = = ρ(water)Vg - ρ(balsa)Vg= =Vg[ρ(water) - ρ(balsa)] = =0.25³•9.8(1000 – 160)=129 N
July 29, 2013

physics
p=p₀+ρgh= 1.013•10⁵ + 800•9.8•18 = =2.42•10⁵ Pa
July 29, 2013

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
July 29, 2013

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
July 29, 2013

physics
N=L/λ =Lf/v =10•215/130=16.5 => 16
July 29, 2013

physics
f=f₀/{1 – (v/u)}=960/{1- (34/343)} = =1065 Hz
July 29, 2013

physics
T=2πsqrt(L/g), g=4π²L/T²=4π²•0.171/0.833² =...
July 29, 2013

physics
7.7•x = 53• 1 x=53/7.7 =6.88 m
July 29, 2013

physics
N=(n₂²-n₁²)/2a=(186²-226²)/(-2•6.4)= =1287.5 rev
July 29, 2013

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)
July 29, 2013

physics
0=N-m₁g => N = m₁g 0=T-F(fr) => T=F(fr)=μN= μ•m₁g 0=T-m₂g => T= m₂g -------- μ•m₁g = m₂g μ = m₂g/m₁g= 50/100 =0.5
July 29, 2013

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