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  1. S

    Supersonic plane at mach 3

    So what equation do you suggest I can use to start up the problem?
  2. S

    Supersonic plane at mach 3

    Homework Statement A supersonic plane flies at Mach 3 at an altitude of 20,000 m. A person on the ground sees the plane directly overhead. How much time passes the before she hears the sonic boom? Homework Equations f=fo(v+-vo/v-+vs) The Attempt at a Solution I don't really know...
  3. S

    Humphrey the Singing Whale and his mate Matilda.

    Homework Statement Humphrey the Singing Whale and his mate Matilda swim toward each other, with Matilda swimming twice as fast as Humphrey. When Humphrey sings a note of a frequency 299 Hz. Maltida hears a frequency of 302 Hz. How fast is Humphrey swimming? (The speed of sound i sea water is...
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    Find the displacement.

    Never mind what i was doing was wrong i was subtracting .18-90 and the sine of that time 0.2m is .199m but what hypnosam is doing seems right I did y= 0.2sin[0.18(0)+90(0)-pi/4] but i just don't know how he got 0.707 when inmy calculator i get 0.013 for sin(-pi/4) wth.
  5. S

    Find the displacement.

    the displacement can't be 0 because the answer sheet says is -.141m and when i put x=0 i still get the same asnwer -0.199m don't get it.
  6. S

    Find the displacement.

    Homework Statement y=0.2msin[(0.18rad/m)x+(90 rad/s)t - pi/4] What is the displacement at position x=0 and t=0? Homework Equations y(x,t)=Asin(kx-wt+phi) The Attempt at a Solution y=0.2m[0.18-90]=-0.199m the answer is -.141 m help?
  7. S

    Calculate the work done according to the graph.

    Homework Statement Calculate the work done by a gas as it slowly expands from point A to point B on the pV diagram shown. Homework Equations Work=PΔV The Attempt at a Solution I calculatate the area under the curve and added both of the areas and I came up with 8*10^11 J and the...
  8. S

    Latent Heat and phase changes (difficult)

    Homework Statement 10g of ice at 0 degrees Celcius is combined with 2 g of steam at 100 degrees Celcius. Find the final temperature of the resulting water. Homework Equations mc(Tf- Ti) m(Lf) or m (Li) The Attempt at a Solution ΔQice=mLice+mcwaterTf...
  9. S

    How much heat is released from water into ice.

    got it!! i found the mistakes ! thanks! :D
  10. S

    How much heat is released from water into ice.

    OK this is what I'm doing 1. cool to freezing point q=(.250kg)(4186J/kgK)(273K-283K)=-1.046*10^4J 2.Freeze MLf=(.250)(3.33*10^5)=8.32*10^4 J 3.Cool to final temp Q= (.250kg)(2090j/kgK)(-283K-273K)=-2.90510*10^5 so when i sum up Q1+mLf+Q2= -2.177*10^5 J Like seriously what am i doing wrong?
  11. S

    How much heat is released from water into ice.

    Homework Statement How much heat is released when 250 g of water at 10 degrees celcius freezes into ice and cools to -10 degrees celcius? Homework Equations Q=mcΔt The Attempt at a Solution q= (250g)(4186)(283-273)=1.046*10^4 J than q=(250g)(2090)(263-283)=-1.045*10^4 J when i subtract...
  12. S

    How long will it take to fill a tank?

    yep just got it!! 45.2 secs thanks!!
  13. S

    How long will it take to fill a tank?

    Q=vA= (12 m/s)(0.3318 m2)= 3.98 m3 s-1 and the equation is Q=V/t???
  14. S

    How long will it take to fill a tank?

    however, is volumteric flow correct to approach this problem?
  15. S

    How long will it take to fill a tank?

    ah! so it really doesnt matter which end i use because they are both going to have the same volumetric flow???
  16. S

    How long will it take to fill a tank?

    Hmmm can you be more specific?
  17. S

    How long will it take to fill a tank?

    Homework Statement The water from a pipe flows into a tank of volume 180 m3. If the tank is initially empty, how long will it take to fill the tank? Homework Equations Q=vA v1=12m/s v2=22m/s A2=0.180982 m2 A1=0.3318 m2 The Attempt at a Solution This question is the third...
  18. S

    What is the pressure at 80 m below the surface of the ocean.

    You were right! THANKS MAN!! I could solve both of them! thanks again!
  19. S

    What is the pressure at 80 m below the surface of the ocean.

    Homework Statement a) A sailor uses a rope to lower an iron ball of radius 30 cm a to a depth of 80 m below the surface of the ocean. What is the pressure (in atm) at that depth? b) Find the tension in the rope in the previous problem. The density of iron is 7.86 *103 Kg/m3. Homework...
  20. S

    A Christmas tree ball hangs from a hook in the ceiling.

    true true i got it! thanks! it was complicated.
  21. S

    A Christmas tree ball hangs from a hook in the ceiling.

    Homework Statement A Christmas tree ball hangs from a hook in the ceiling. If the radius of the ball is 8 cm, find the period of the ball's oscillation as it swings on the hook. Homework Equations T=2pi*√L/g The Attempt at a Solution I tried pluggin the number and i'm way off...
  22. S

    What is the period of oscillation of the mass on the spring?

    than for the second part I used A=VmaxT/2pi and got the right amplitude too.
  23. S

    What is the period of oscillation of the mass on the spring?

    Got it!!!! yeah i really didn't have to use any angular velocities. The hard part was assuming that the mass is 1 kg. because it only mentions mass and they don;t mention anything else so i tried 1 kg just for curiosity. I used T=2pi*sqrt(m/k) i knew that k=F/deltay so (1kg)(9.8)/0.03m=326.7...
  24. S

    What is the period of oscillation of the mass on the spring?

    Homework Statement a)When a mass is attached to the end of a vertical spring, the spring is stretched down 3 cm. If the mass is pulled down a bit farther and then released, what is the period of oscillation of the mass on the spring? b) if the mass moves through its equilibrium position at 50...
  25. S

    Velocity of an apple before strikes the surface of a white dwarf.

    The thing is that i don't think this problem should be base with integrals, it has to be an easier way, sqrt(3.27*106)(12.8*106+6.37*106) and still i don't get the right answer. I mean there has to be another factor that I am not taking into account. I know this problem does not need integrals.
  26. S

    Velocity of an apple before strikes the surface of a white dwarf.

    yes a=Gm/r^2 that's how i got the acceleration of the white dwarf The radius is equal of the earth's radius which is 6.37*10^2 and the mass was the same the sun which was 1.99*10^30. However, I still don't understand your question.
  27. S

    Velocity of an apple before strikes the surface of a white dwarf.

    Homework Statement An apple is dropped from a height of 12.8*10^6 m above the surface of the white dwarf. With what speed does the apple strike the surface of the white dwarf? M of white dwarf= 1.99*10^30 gravity of white dwarf= 3.29*10^6 Homework Equations Vf^2=Vi^2+2a(deltaX)...
  28. S

    Find final angular velocity.

    LOL no. So the KEf is 0 after all? I thought it was 0 because after the collision they both have no kinetic energy because they have no velocity. They both come to a stop. Don't know if my reason is indeed correct.
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