Physics help?

Polk addict
Polk addict Posts: 558
edited September 2009 in The Clubhouse
Since like last week, someone else was able to get physics help from someone, I hope the someone would be kind enough to help me...


Ok, so with these two problems, I think I can finish the rest...


1.
During a baseball game a fly ball is hit to center field and is caught 132 m from home plate. Just when the ball is caught, a runner on third base takes off for home, and the center fielder throws the ball to the catcher standing on home plate. The runner takes 3.90 s to reach home, while the baseball is thrown with a velocity whose horizontal component is 47 m/s. Which reaches home first, the runner or the ball, and by how much time?

2.

A diver springs upward from a board that is three meters above the water. At the instant she contacts the water her speed is 9.00 m/s and her body makes an angle of 75.0° with respect to the horizontal surface of the water. Determine her initial velocity, both magnitude and direction.


:confused:
Chiranth
hoosier21 wrote:
Cobra + SDA's = dead amps laying all around.
Post edited by Polk addict on
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  • Polk addict
    Polk addict Posts: 558
    edited September 2009
    Ok, maybe I might be getting this... I got 16.16 m/s by subsitituting Vosin(60) as Vo...

    Edit: Wrong Problem...
    Chiranth
    hoosier21 wrote:
    Cobra + SDA's = dead amps laying all around.
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  • Cpyder
    Cpyder Posts: 514
    edited September 2009
    1. Assuming frictional loses on the ball to be negligible, this is a fairly straight forward problem. Even though the ball will fly in a parabolic path, the horizontal component is all that matters for this problem. To solve for this all you need to do is find the ball's flight time. Time = distance traveled/velocity. Plug and chug brotha!
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  • nooshinjohn
    nooshinjohn Posts: 25,446
    edited September 2009
    does m stand for meters?
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    “When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson
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  • Cpyder
    Cpyder Posts: 514
    edited September 2009
    2. First, break her velocity into its component vectors when she contacts the water. Make a right triangle with a 75 degree angle with the hypotenuse = 9 m/s. Solve for the two legs using trig. X (which is horizontal position) = cos (75 degrees). Y = sin (75 degrees). Remember the horizontal (X) velocity is constant since friction = 0 and gravity only acts in the Y (vertical) direction. So you've got the X dir down...
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  • Cpyder
    Cpyder Posts: 514
    edited September 2009
    nooshinjohn wrote: »
    does m stand for meters?

    Yes it does
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  • nooshinjohn
    nooshinjohn Posts: 25,446
    edited September 2009
    in your first question, 132m is close to 450 feet, It's high and deep fly ball to Center and all the center fielder can do is look up and kiss that one GOODBYE!!! That one is LOOOONG GONE!!! A home run and the game is over!:D:p
    The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD

    “When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson
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  • Cpyder
    Cpyder Posts: 514
    edited September 2009
    After you solve for the y velocity, use the formula:
    2 x Acceleration due to gravity x distance = (final velocity)^2 - (initial velocity)^2

    You can use 3m for distance because although her total flight was longer than 3m, her vertical velocity will be the same when she leaves the board and on her way back down into the water at the board. (Although, the sign will be different.) Solve for initial velocity
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  • Cpyder
    Cpyder Posts: 514
    edited September 2009
    Make a new triangle with your two velocities you found and solve for the angle to find direction.

    Bingo Bango! Good luck
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  • Polk addict
    Polk addict Posts: 558
    edited September 2009
    Cpyder wrote: »
    2. First, break her velocity into its component vectors when she contacts the water. Make a right triangle with a 75 degree angle with the hypotenuse = 9 m/s. Solve for the two legs using trig. X (which is horizontal position) = cos (75 degrees). Y = sin (75 degrees). Remember the horizontal (X) velocity is constant since friction = 0 and gravity only acts in the Y (vertical) direction. So you've got the X dir down...

    This becomes 3.73 for velocity... Which doesn't seem to be the answer... I'm taking this thing online, so it tells me when I'm wrong, and I get four submissions...

    Maybe not getting help will help me since I have a test tomorrow... :(
    Chiranth
    hoosier21 wrote:
    Cobra + SDA's = dead amps laying all around.
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  • Polk addict
    Polk addict Posts: 558
    edited September 2009
    Cpyder wrote: »
    After you solve for the y velocity, use the formula:
    2 x Acceleration due to gravity x distance = (final velocity)^2 - (initial velocity)^2

    You can use 3m for distance because although her total flight was longer than 3m, her vertical velocity will be the same when she leaves the board and on her way back down into the water at the board. (Although, the sign will be different.) Solve for initial velocity

    Woot!! Same equation I was given...

    Thanks for the help!
    Chiranth
    hoosier21 wrote:
    Cobra + SDA's = dead amps laying all around.
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  • Cpyder
    Cpyder Posts: 514
    edited September 2009
    Polk addict wrote: »
    Woot!! Same equation I was given...

    Thanks for the help!

    You're welcome.

    Some other pointers.

    If you're using a graphing calculator, make sure it's in degrees mode.
    Look at the picture and orientation of your axis. What your signs!
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