Wednesday
October 26, 2016

# Posts by elena

Total # Posts: 4,384

Physics
x: mgsinα = F(fr) y: N=mgcosα + F mgsinα = F(fr) =μN =μ(mgcosα + F), F =mgsinα/μ - mgcosα = =mg(sinα/μ – cosα)
October 7, 2013

physics
âsin53/sin 90 = n/n(gl) n=n(gl) •sin53=1.47•0.8=1.17
October 7, 2013

Physics/Electricity
October 6, 2013

Physics/electricity
T= 2πR/v, I=e/T=ev/2πR= =1.6•10⁻¹⁹•5.48•10⁵/2•π•2.12•10⁻¹º= =6.58•10⁻⁵A
October 6, 2013

Physics/electricity
resistivity at 20℃ is ρ=22•10⁻⁸ Ohm•m R= ρL/A= 4ρL/πD²= =2•22•10⁻⁸•19/ π(1.024•10⁻³)²= =5.076 Ohms
October 6, 2013

Physics
q =E/U =0.1/19•10⁶ =5.26•10⁻⁹ C
October 6, 2013

Physics
http://www.physics.brocku.ca/Courses/1P22_DAgostino/samples/Ch21P.pdf SP37 page 24
October 6, 2013

physical science
mgh/2=mcΔT For iron c=444 J/kg•K ΔT=gh/2c = 9.8•90/444•2=0.99℃
October 6, 2013

college physics
E=k2λ/r E=9•10⁹•2•87•10⁻⁶/2•0.1 =... E=9•10⁹•2•87•10⁻⁶/2•0.26 =... E=9•10⁹•2•87•10⁻⁶/2•1.4 =...
October 6, 2013

physics
The time to rich the highest point is tₒ= 2vₒ•sinα/2g =2•20•sin35/2•10 =1.15 s The time for covering the distance to the wall ‚d’ is t₁=d/vₒ•cosα =15/20•cos35= 0.92 s At horizontal distance d from the ...
October 6, 2013

physics
v⒳=v₀•cosα=10.02m/s v⒴=v₀•sinα=29.44 m/s a(x)=0 a(y)= -g
October 6, 2013

Physics
v=0.197m/s (?!?!) => t=s/v =5000/0.197 =25381 s=7.05 h (?!?!)
October 6, 2013

PHYSICS
The time to rich the highest point is tₒ= 2vₒ•sinα/2g =2•20•sin35/2•10 =1.15 s The time for covering the distance to the wall ‚d’ is t₁=d/vₒ•cosα =15/20•cos35= 0.92 s At horizontal distance d from the ...
October 6, 2013

physics(help)
The time to rich the highest point is tₒ= 2vₒ•sinα/2g =2•20•sin35/2•10 =1.15 s The time for covering the distance to the wall ‚d’ is t₁=d/vₒ•cosα =15/20•cos35= 0.92 s At horizontal distance d from the ...
October 6, 2013

PHYSICS
E=σ/2ε₀=2.05•10⁻⁶/2•8.85•10⁻¹²=1.16•10⁵
October 6, 2013

Physics
The time to rich the highest point is tₒ= 2vₒ•sinα/2g =2•20•sin35/2•10 =1.15 s The time for covering the distance to the wall ‚d’ is t₁=d/vₒ•cosα =15/20•cos35= 0.92 s At horizontal distance d from the ...
October 6, 2013

physics
The time to rich the highest point is tₒ= 2vₒ•sinα/2g =2•20•sin35/2•10 =1.15 s The time for covering the distance to the wall ‚d’ is t₁=d/vₒ•cosα =15/20•cos35= 0.92 s At horizontal distance d from the ...
October 6, 2013

physics
θ=θ(max) •sin(ωt+α) dθ/dt =θ(max) •ω•sin(ωt+α) (dθ/dt)(max) = θ(max)•ω= θ(max)√(g/L) v(max) =(dθ/dt)(max) •L = L•θ(max)√(g/L)
October 6, 2013

Physics
R=0.5 m W= mg mg =F(buoyant) W = (1/2) •(4πR³/3) •ρ•g = =1000•4π•0.5³•10/2•3= =2618 N
October 5, 2013

physics
ma=T-mg a=(T/m)-g= 19.5 – 9.8 = 9.7 m/s² h=at²/2=> t=2h/a = 2•10/9.7 = 2.06 s.
October 4, 2013

physics
F=ma=mv/t =12.3•10⁻⁶•4/1•10⁻³ =49.2•10⁻³ N F/mg = 49.2•10⁻³/12.3•10⁻⁶•9.8 =408.2
October 4, 2013

physics
r =(0.020m/s³)t ³ i ^ +(2.2m/s)tj ^ −(0.060m/s² )t²k ^. v= dr/dt =(3•0.020m/s³ ) •t²• i ^ +(2.2m/s) • j ^ −2• (0.060m/s² )t•k ^. a=d²r/dt²=(6•0.020m/s ³) •t i ^ -2• (0....
October 4, 2013

physics
The ball moves in projectile motion. When it is moving horizontally, v(y) =0 +x is directed to the right, +y is directed upward, a(x)= 0, a(y) =-g v₀(y)=sqrt(2gh) = sqrt(2•9.8•4) = 8.85 m/s v= v₀(y)-gt At the top point v=0 => t= v₀(y)/g =8.85/9.8...
October 4, 2013

Physics
v(x) =v₀(x) = 50 m/s v₀=84 m/s cosα =v₀(x)/ v₀=50/84 =0.6 α=53.5⁰
October 4, 2013

Physics
F(fr) +mg= F(y) F(y) = Fsinα F(fr) =Fsinα-mg
October 3, 2013

Physics
W=PE+KE+W(fr) =mgh+mv²/2 +W(fr) = =m(gh+ v²/2)+W(fr) =1260(0.6•9.8 +3²/2)+2870 = =13078.8+2870 =15948.8 J
October 3, 2013

Physics
mv²/2 =W(fr) = μNs= μmgs μ=v²/2gs =5.8²/2•9.8•20 =0.086
October 3, 2013

Electricity and Electronics
15. A 19. D
October 3, 2013

physics
d(x)=dcos46⁰=110•cos46⁰=76.4 m. d(y) =- dsin46⁰=- 110•sin46⁰= - 79.1 m. v(x) = vcos28⁰=350•cos28⁰= 309 m/s v(y) = vsin28⁰=350•sin28⁰=164.3 m/s a(x) = 0 a(y) = - 9 m/s²
October 3, 2013

Physics
Magnetic ﬁeld at the center of a circular current-carrying loop of N turns and radius r is B=Nμ₀I/2r….. (1) N=L/2πr ….(2) I=U/R=U/R₀L ….(3) Substitution (2) and (3) in (1) gives B=Nμ₀I/2r = (L/2πr) •(μ&#...
October 3, 2013

Physics
ma=F mv²/R =qvBsinα. v⊥B => sinα = 1. mv/R =qB, R = mv/ qB, T=2πR/v=2π m /qB= = 2π/B(q/m) =2π/0.69•5.7•10⁸0.69= =1.6•10⁻⁸ s
October 3, 2013

Physics
http://einstein.drexel.edu/~wking/courses/phys101_w07/hwk/hwk4.pdf
October 3, 2013

physics
(a) the work done by the applied force W=F(x) •s=F•cos α•s= 18.6•cos23.7•2.09 = …. (b) the magnitude of the normal force exerted by the table N =mg+F(y) =mg+Fsin α = 2.4•9.8 +18.6•sin23.7 = … (c) the magnitude of the force...
October 3, 2013

physics
d=17.7 m vₒ =15.4 m/s α =38.7⁰ =>2 α =77.4⁰ L=vₒ²•sin2α/g=15.4²•sin77.4/9.8 =23.6 m t= 2vₒ•sinα/g=2•15.4•sin38.7/9.8 = 1.97 s. s=(L-d)/t =(23.6-17.7)/1.97 =3 m/s
October 3, 2013

Physicis
Make the route plan s₁= 300 =x₁+x₂ s₂ =395, α =26.5⁰ s₃ = 150 x₃ connects the point of s₂ and s₃ intersection and the point on s₁ which divides s₁ by x₁ and x₂ (x₃ ⊥ s₁) s&#...
October 2, 2013

Physics
(A) L=18.3 m, h=0.809 m h=gt²/2 t=sqrt(2h/g) = .... L=vt => v=L/t=.... (B) h=gt²/2 t=sqrt(2h/g) = … L₁=v₁t =... L₂=v₂t =....
October 2, 2013

physics
d(x)=dcos46⁰=110•cos46⁰=76.4 m. d(y) =- dsin46⁰=- 110•sin46⁰= - 79.1 m. v(x) = vcos28⁰=350•cos28⁰= 309 m/s v(y) = vsin28⁰=350•sin28⁰=164.3 m/s a(x) = 0 a(y) = - 9 m/s²
October 2, 2013

Physics
(A) v=gt t=v/g h=gt²/2 =gv²/2g²=v²/2g (B) mv²/2 = mgh h= v²/2g
October 2, 2013

physics
g=1.6 m/s² Upward motion v=v₀-gt v=0 t= v₀/g=5/1.6 =3.125 s Downward motion t₁=15-3.125 =11.875 m/s v=gt₁=1.6•11.875=19 m/s
October 2, 2013

Physics
F₁ =qvBsinα₁ F₂ =qvBsinα₂ F₂=2.4F₁ F₁/F₂=1/2.4 =qvBsinα₁/qvBsinα₂ sin α₂=2.4•sin α₁ =2.4•sin19⁰=0.78 α₂=51.4⁰
October 2, 2013

v=81.7 km/h =81700/3600=22.7 m/s d= v²/2a=22.7²/300=1.72 m
October 2, 2013

v=81.7 km/h =81700/3600=22.7 m/s d= v²/2a=22.7²/300=1.72 m
October 2, 2013

Physics
6.7 lb = 3.04 kg mg₁=3.04•9.8 =29.8 N mg₂=mg₁/6 =3.04•9.8/6=4.97 N
September 30, 2013

phusics
a=v²/2s F=ma=m v²/2s =2.1•10⁵•30²/2•120 = 787500 N
September 30, 2013

phys223
September 30, 2013

physics
v =at => a=v/t P=W/t = Fs/t=Fv = ma•v= mv²/t
September 30, 2013

physics
KE=PE mv₀²/2=mgh=mgxsinα x= v₀²/2gsinα=3²/2•9.8•sin22=1.23 m. a₁=v₀²/2x =9/2•1.23=3.66 m/s² Upward v= v₀-a₁t₁ v=0 t₁=v₀/a₁=3/3.66=0.82 s. Downward PE=KE mgxsinα= ...
September 30, 2013

physics
September 26, 2013

Physics
An initial velocity of the projectile v₀ = the velocity of the plane. v₀ (x) = v₀cosα, v₀ (y) = v₀sinα, h= v₀ (y) •t+ gt²/2= =v₀sinα•t + gt²/2. v₀={h- gt²/2}/ sinα•t= ={790 –...
September 26, 2013

science
p=mg/A = 50•9.8/2(0.15•0.005)= =326666 Pa
September 26, 2013

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
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 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