Results 1 to 4 of 4

Thread: [SOLVED] ideal projectile motion (vectors) calc3

  1. #1
    Member
    Joined
    Apr 2008
    Posts
    171

    [SOLVED] ideal projectile motion (vectors) calc3

    travel time:
    a projectile is fired at a speed of 840 m/sec at an angle of 60 degree. how long will it take to get 21km downrange?



    here is what i did an its no where close to right. the answer was 50seconds i got no ideal how to get that. here is what i attempted to do.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Like a stone-audioslave ADARSH's Avatar
    Joined
    Aug 2008
    From
    India
    Posts
    726
    Thanks
    2
    $\displaystyle
    v_0 = 840m/s
    $

    $\displaystyle
    \alpha=60~degrees
    $

    $\displaystyle 21km=21000m$

    Now Lets take horizontal component of velocity which remains constant
    (as the gravity is vertical)
    So
    $\displaystyle
    V_x= Vcos(60) = \frac{v}{2}
    $

    Thus in time t the distance travelled
    $\displaystyle = \frac{v}{2} \times t$

    Now look the distance travelled horizontally is known as Downrange

    Thus

    $\displaystyle \frac{840}{2} \times t= 21000$

    Can you go ahead
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Apr 2008
    Posts
    171
    Quote Originally Posted by ADARSH View Post
    $\displaystyle
    v_0 = 840m/s
    $

    $\displaystyle
    \alpha=60~degrees
    $

    $\displaystyle 21km=21000m$

    Now Lets take horizontal component of velocity which remains constant
    (as the gravity is vertical)
    So
    $\displaystyle
    V_x= Vcos(60) = \frac{v}{2}
    $

    Thus in time t the distance travelled
    $\displaystyle = \frac{v}{2} \times t$

    Now look the distance travelled horizontally is known as Downrange

    Thus

    $\displaystyle \frac{840}{2} \times t= 21000$

    Can you go ahead

    ok so 21000 * 2 = 42k / 840 = 50

    i have no idea what equation you used to get that though..

    the book gives a eqaution:

    (2v sin(alpha)) /g = t

    not sure what equation u used?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Like a stone-audioslave ADARSH's Avatar
    Joined
    Aug 2008
    From
    India
    Posts
    726
    Thanks
    2
    Quote Originally Posted by Legendsn3verdie View Post
    ok so 21000 * 2 = 42k / 840 = 50

    i have no idea what equation you used to get that though..

    the book gives a eqaution:


    not sure what equation u used?
    -First of all You must know that velocity is in the form as

    $\displaystyle
    V^2= (vsin(\theta))^2+(vcos(\theta))^2
    $

    -Now The term $\displaystyle vsin(\theta)$ is the value of velocity in the y direction(vertical direction)
    (use trignometry)

    -similarly $\displaystyle vcos(\theta)$ is the value of velocity in the x(horizontal) direction

    -Now the velocity in x direction remains constant and its value in y direction is affected by acceleration

    - Since we were given
    +the value of velocity
    + the value of alpha
    + the horizontal distance covered (distance travelled by $\displaystyle V_x$ ONLY)

    -We can use the general formula that

    $\displaystyle
    Velocity~\times ~time=~distance
    $

    ie;

    $\displaystyle
    V_x ~\times t = 21000m
    $

    Watch the diagram and this link
    Attached Thumbnails Attached Thumbnails [SOLVED] ideal projectile motion (vectors) calc3-components.bmp  
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Projectile Motion
    Posted in the Calculus Forum
    Replies: 3
    Last Post: May 21st 2010, 04:52 PM
  2. [SOLVED] Physics - Projectile Motion, Vectors
    Posted in the Advanced Math Topics Forum
    Replies: 2
    Last Post: Feb 3rd 2010, 07:10 PM
  3. [SOLVED] Physics - Projectile Motion (2d), Vectors
    Posted in the Math Topics Forum
    Replies: 3
    Last Post: Jan 30th 2010, 08:47 AM
  4. Projectile motion and Vectors
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: Aug 2nd 2009, 03:53 AM
  5. calc3 (projectile motion)
    Posted in the Calculus Forum
    Replies: 1
    Last Post: Feb 15th 2009, 01:44 PM

Search Tags


/mathhelpforum @mathhelpforum