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Homework Help: Projectile Motion maximum height

  1. Dec 3, 2007 #1
    1. http://img525.imageshack.us/img525/6376/fic11p112xe1.png [Broken]
    http://img525.imageshack.us/img525/9550/vqc11p112el8.png [Broken]

    2. d = 1/2at^2 + v1t

    v =d/t

    horizontal time it takes equals vertical time

    t = d/v = 50 /(v1cos10)

    d = 1/2at^2 + v1t
    -0.6 = 1/2(-9.81)(50/v1cos10)^2 + v1sin10(50 /(v1cos10)

    i get v1 = 36.6 m/s

    -1.6 = 1/2(-9.81)(50/v1cos10)^2 + v1sin10(50 /(v1cos10)
    i get v1 = 34.8 m/s

    So my range is 34.8 m/s to 36.6 m/s

    for b part

    dv = v1(t) - 1/2(9.81)(t^2)

    maximum height occurs at half the time so i used 1/2(50/v1cos10)

    dv = 34.8(1/2(50/36.64cos10) - 1/2(9.81)(1/2(50/34.8cos10))^2
    i got 22.8 m

    for 2nd velocity

    dv = 36.64(1/2(50/36.64cos10) - 1/2(9.81)(1/2(50/36.64cos10))^2
    i got 23.0 m

    So my maximum height range is 22.8 m to 23.0 m

    According to my online assignment this is wrong

    plz helppppppppppp

    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Dec 3, 2007 #2

    i just noticed for maximum height i guess I also add 2.1 m if they are measuring from the Ground so 22.8 + 2.1 = 24.9 m and 23.0 + 2.1 = 25.1 m but these values still are somehow wrong........
  4. Dec 3, 2007 #3
    i know it may be a little long in calculating but can someone check to see if my process is right if no one wnats to check my calculations :)
  5. Dec 3, 2007 #4
    Hi Salman, i have been doing some work on this problem, Would you please be so kind to include the correct answers so i can verify and post it?
  6. Dec 4, 2007 #5
    if i had the correct answers i wouldnt have posted it :(

    wat answers did u get? and how did u attempt this problem differently?

  7. Dec 4, 2007 #6
    vipul did u get different answerS?
  8. Dec 4, 2007 #7
    sorry salman, havent got the answers yet but still working on them, i thought if u had the correct answers, maybe we can work backwards.
  9. Dec 5, 2007 #8
    hmm ok if u get answers tell me because i can keep submitting the answers repeatedly on my assignemtnt o see if they are right but I need the right answer. I dont understand what Im doing WRONG!!!!!!!!!!!!!!!

    also do u have a energy question? about a spring and stuff? Did u fnish that one :S?
  10. Dec 5, 2007 #9
    Salman, for part (a), my answers; the range is between 34.99m/s to 36.82m/s. Could you please verify these?
  11. Dec 6, 2007 #10
    hmm its one question so try getting b part too about maximum height range,

    like its ONE question


    and u have to enter both answers.

    then i can cehck if they are right,

    if someone else can check my solution plz do, i dont know where im going wrong!
  12. Dec 8, 2007 #11
    Ok, my answers;

    a) 34.99m/s to 36.82m/s
    b) 3.99m to 4.18m
  13. Dec 8, 2007 #12
    lol its too late sry my assignments done
  14. Dec 8, 2007 #13
    Did u get the correct answers?
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