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Homework Help: Problems about Projectile Motion

  1. Sep 3, 2007 #1


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    Hey guys, Im taking an AP physics course and I'm fairly new to this challenging physics. If you could please explain how to the get the answer so that even a newbie like me can understand, I would be so grateful.

    1. Romeo is chucking pebbles gently up to Juliet's window, and he wants the pebbles to hit the window with only a horizontal component of velocity. he is standing at the edge of a rose garden 8.0 meters below her windows and 9.0 meters from the base of the wall. How fast are the pebbles going when they hit her window?

    2. A ball thrown horizontally at 22.2. m/s from the roof of a building lands 36.0 meters from the base of the building? What is it's height?

    3. A shot-putter throws the shot with an initial speed of 14 m/s at a 40 degree angle to the horizontal. Calculate the horizontal distance traveled by the shot if it leaves the athlete's hand at a height of 2.2 m above the ground?

    4. AN athlete executing a long jump leaves the ground at a 30 degree angle and travels 7.8 meters. What was the takeoff speed? If this speed were increased by 5 percent, how much longer would the jump be by?

    5. A hunter aims directly at a level target 120 m away. If the bullet leaves the gun at a speed of 250 m/s, by how much will it miss the target. At what angle should the gun be aimed so the target will be hit?

    6. A projectile is fired with an initial speed of 75.2 m/s at an angle of 34.5 above the horizontal on a long flat firing range. Determine the maximum height reached by the projectile, the total time in the air, the total horizontal distance covered (the range) and the velocity of the projectile 1.5 s after firing.

    Please help me in trying to solve these problems.
    Reply ASAP, thanks.
  2. jcsd
  3. Sep 3, 2007 #2


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    Homework Helper

    Hi 7up,

    Forum rules state you must show some work in order to get help. What are your thoughts on the first question? Can you elaborate on where you are having trouble? Take a look at this site and see if it helps you out a bit: http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html Click on Mechanics, then Velocity and Acceleration, then Trajectories to get to the information more specific to your homework.
    Last edited: Sep 3, 2007
  4. Sep 3, 2007 #3
    hmm..projectile motion...
    i advise you to learna and master the basics of the subject first before trying to do the questions. ok lets see if you can understand the subject than these problems should not be much of a challenge.. oh and have a calculator with you while you are trying the questions. it will come in useful!
    yea and i agree with hage567 that you should visit the website for help
    maybe you can show us some of your attempts of the questions and then show it to uss for us to justify them. =)
    (visit my blog!)
    Last edited: Sep 3, 2007
  5. Mar 30, 2008 #4


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    Staff Emeritus
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    Mr. Survive,

    The purpose of the Homework forums is to assist students with their homework problem, not to give out complete solutions. Yes it is possible that a student may gain some conceptual understanding from reading solutions, but it is much better to guide a student to the correct solution without giving it them outright. Furthermore, unscrupulous students may simply copy the solutions verbatim without ever understanding the concept, this is both bad for the student's education and for the reputation of PF. Many of the poster's here are tutors or professors themselves and would take offense to find that websites were giving homework solutions to students.

    Whilst we appreciate your help here in the Homework forums, I would like to remind you of the Physics Forums Global Guidelines, which you agreed to upon registration,

  6. Mar 30, 2008 #5

    Doc Al

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    Staff: Mentor

    Note: I have deleted the complete solutions provided by new member mr.survive. As Hootenanny points out, posting complete solutions is against PF rules.
  7. Jan 20, 2011 #6
    i tried to solve problem number 2 given above, and using the formula given by our professor i came up with this answer, height=12.89m..:confused: is this correct?

    given the ff. formulas:

    time=SQRT of (twice the height / g )

    Range=initial velocity x time
  8. Jan 20, 2011 #7

    Doc Al

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    Staff: Mentor

    Looks OK to me.
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