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    pilar22's Avatar
    pilar22 Posts: 8, Reputation: 1
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    #1

    May 23, 2008, 10:58 PM
    Velocity questions
    A football is thrown with an initial upward velocity component of 15.0 and a horizontal velocity component of 18.0 .


    How high does it get above the ground?
    How much time after it is thrown does it take to return to its original height?
    How far has the football traveled horizontally from its original position?
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    pilar22 Posts: 8, Reputation: 1
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    #2

    May 23, 2008, 11:01 PM
    Velocity velocity velocity
    A tennis player hits a ball at ground level, giving it an initial velocity of 28.0 at 52.0 above the horizontal.

    What are the horizontal and vertical components of the ball's initial velocity?
    How high above the ground does the ball go?
    How long does it take the ball to reach its maximum height?
    What is the ball's velocity at its highest point?
    What is the ball's acceleration at its highest point?
    For how long a time is the ball in the air?
    When this ball lands on the court, how far is it from the place where it was hit?
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    pilar22 Posts: 8, Reputation: 1
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    #3

    May 23, 2008, 11:03 PM
    Magnitudes & velocity
    A man stands on the roof of a 10.0 -tall building and throws a rock with a velocity of magnitude 24.0 at an angle of 34.0 above the horizontal. You can ignore air resistance.

    Calculate the maximum height above the roof reached by the rock.
    Calculate the magnitude of the velocity of the rock just before it strikes the ground.
    Calculate the horizontal distance from the base of the building to the point where the rock strikes the ground.
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    pilar22 Posts: 8, Reputation: 1
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    #4

    May 23, 2008, 11:03 PM
    Speed and acceleration
    You swing a 3.00 stone in a circle, using the full length of a thin 65.0 rope.

    At what speed should you swing it so its acceleration will be 9.8 ?
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    pilar22 Posts: 8, Reputation: 1
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    #5

    May 23, 2008, 11:06 PM
    Angles, magnitudes and velocity
    A baseball thrown at an angle of 55.0 above the horizontal strikes a building 17.0 away at a point 7.00 above the point from which it is thrown. Ignore air resistance.

    Find the magnitude of the initial velocity of the baseball (the velocity with which the baseball is thrown).

    Find the magnitude of the velocity of the baseball just before it strikes the building.

    Find the direction of the velocity of the baseball just before it strikes the building.
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    pilar22 Posts: 8, Reputation: 1
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    #6

    May 23, 2008, 11:07 PM
    Trajectory. Angle
    A firefighting crew uses a water cannon that shoots water at 25.0 at a fixed angle of 53.0 above the horizontal. The firefighters want to direct the water at a blaze that is 10.0 above ground level.


    How far from the building should they position their cannon? There are two possibilities (); can you get them both? (Hint: Start with a sketch showing the trajectory of the water.)
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    Curlyben Posts: 18,514, Reputation: 1860
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    #7

    May 23, 2008, 11:14 PM
    Questions merged and moved.

    Please refer to this announcement: https://www.askmehelpdesk.com/math-s...-b-u-font.html
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    Capuchin Posts: 5,255, Reputation: 656
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    #8

    May 23, 2008, 11:25 PM
    The basic method you should be using here is to split the motion of the object into x and y components. Then applying the equations of motion for x and y motion separately. You can always work out the resultant vector at the end again!
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    galactus Posts: 2,271, Reputation: 282
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    #9

    May 24, 2008, 05:14 PM
    I will help with this one and you try the others. If you get stuck, write back. I doubt if you respond back at all anyway, but here goes. You did not specify units, so I will use feet.

    Quote Originally Posted by pilar22
    A tennis player hits a ball at ground level, giving it an initial velocity of 28.0 at 52.0 above the horizontal.
    What are the horizontal and vertical components of the ball's initial velocity?
    Horizontal component:

    Vertical component:

    How high above the ground does the ball go?
    The max height is achieved when dy/dx=0



    Solve for t and we get

    Plug this into y and get 7.61 feet

    How long does it take the ball to reach its maximum height?
    As showed before, 69 sec.

    What is the ball's velocity at its highest point?
    The velocity is 0 at the highest point.

    For how long a time is the ball in the air?
    Set it equal to 0 and solve the y component for t. You get two values. The good one is 1.38 seconds

    When this ball lands on the court, how far is it from the place where it was hit?
    Plug the previous answer into the x component and get 23.77 feet
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    pilar22 Posts: 8, Reputation: 1
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    #10

    May 24, 2008, 05:47 PM
    All these answers were wrong because they aren't in feet. I need big time help! Thanks in advance


    Quote Originally Posted by galactus
    I will help with this one and you try the others. If you get stuck, write back. I doubt if you respond back at all anyway, but here goes. You did not specify units, so I will use feet.





    Horizontal component:

    Vertical component:



    The max height is achieved when dy/dx=0



    Solve for t and we get

    Plug this into y and get 7.61 feet



    As showed before, .69 sec.



    The velocity is 0 at the highest point.



    Set it equal to 0 and solve the y component for t. You get two values. The good one is 1.38 seconds



    Plug the previous answer into the x component and get 23.77 feet
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    galactus Posts: 2,271, Reputation: 282
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    #11

    May 24, 2008, 06:00 PM
    If it's in metric then just change the gravity constant from 16 to 4.9 and recalculate using the same formulas.
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    Capuchin Posts: 5,255, Reputation: 656
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    #12

    May 24, 2008, 06:02 PM
    Quote Originally Posted by pilar22
    All these answers were wrong because they aren't in feet. I need big time help! Can you please email me at [email protected]. Thanks in advance
    We aren't here to do your work for you. Galactus gave you a sample answer, use it to answer the rest. They're all very similar.

    Let us know if you get stuck.
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    pilar22 Posts: 8, Reputation: 1
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    #13

    May 24, 2008, 06:07 PM
    It still keeps giving me the wrong answer.. can u further help me? PLEASE!!








    Quote Originally Posted by galactus
    If it's in metric then just change the gravity constant from 16 to 4.9 and recalculate using the same formulas.
    Rehaan_genius's Avatar
    Rehaan_genius Posts: 49, Reputation: 1
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    #14

    Aug 11, 2008, 01:06 AM
    All the questions asked by pilar22 are from projectile and circular motion(Kinematics).
    I will suggest him to again go through all the theory section of these two topics cause the questions are not so difficult and also trying again and again will help to build up the concept and if still you can't do them then ask!

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