Results 1 to 7 of 7

Math Help - Rocket in the Air

  1. #1
    Newbie
    Joined
    Apr 2010
    From
    NJ
    Posts
    13

    Rocket in the Air

    A rocket is fired straight up from the ground with an initial velocity of 900 feet per second.

    (a) How long does it take the rocket to reach 4200 feet?


    (b) When will the rocket hit the ground?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member Anonymous1's Avatar
    Joined
    Nov 2009
    From
    Big Red, NY
    Posts
    517
    Thanks
    1
    Quote Originally Posted by emfn96 View Post
    A rocket is fired straight up from the ground with an initial velocity of 900 feet per second.

    (a) How long does it take the rocket to reach 4200 feet?
    Solve.

    \frac{900ft}{1\times seconds} = \frac{4200ft}{x\times seconds}

    Wait...

    You need to incorporate gravity...
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Apr 2010
    From
    NJ
    Posts
    13

    No Gravity

    Quote Originally Posted by Anonymous1 View Post
    Solve.

    \frac{900ft}{1\times seconds} = \frac{4200ft}{x\times seconds}

    Wait...

    You need to incorporate gravity...
    The question does not say to include gravity. Is any equation needed to solve this question?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member Anonymous1's Avatar
    Joined
    Nov 2009
    From
    Big Red, NY
    Posts
    517
    Thanks
    1
    Quote Originally Posted by emfn96 View Post
    The question does not say to include gravity. Is any equation needed to solve this question?
    Well if there was no gravity the rocket would never come down...
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Apr 2010
    From
    NJ
    Posts
    13

    Math Question Not Physics

    Quote Originally Posted by Anonymous1 View Post
    Well if there was no gravity the rocket would never come down...
    This question was taken from a precalculus book not a physics text or course. Can you give me more detail?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Super Member Anonymous1's Avatar
    Joined
    Nov 2009
    From
    Big Red, NY
    Posts
    517
    Thanks
    1
    You need to use newton's third law of motion...

    (v_2)^2 =(v_1)^2 + 2as

    s= max height height rocket ascends
    a= acceleration due to gravity (32.1522 ft/s it is negative as it is accting downward)
    v_1= initial vel(900 ft/s)
    v_2= final vel(0 m/s at top pos it doesnt have velocity)

    Where t= time in the air.

    (v2) = (v1) + at
    Last edited by Anonymous1; April 5th 2010 at 09:49 PM.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,791
    Thanks
    1531
    This is, in my opinion, a really bad problem. The equation Anonymous1 gives, as well as s= -gt^2+ v_0t+ s_0 will work for something thrown upward so that the only force is that of gravity. But the whole point of a rocket is that it continues firing as it goes up so that is NOT true.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Rocket Equation
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: June 11th 2011, 04:46 PM
  2. a rocket issue
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 28th 2010, 06:09 PM
  3. Rocket Launching
    Posted in the Advanced Math Topics Forum
    Replies: 2
    Last Post: May 11th 2010, 11:35 AM
  4. A Rocket in the Air
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: December 8th 2009, 01:59 AM
  5. rocket in my pocket
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: January 8th 2007, 09:33 AM

Search Tags


/mathhelpforum @mathhelpforum