Results 1 to 9 of 9

Math Help - Work on a inclined plate problem

  1. #1
    Junior Member silvercats's Avatar
    Joined
    Mar 2011
    Posts
    67

    Work on a inclined plate problem

    8kg object is dragged 25m distance on a 30 degrees
    inclined plate.if the friction coefficient is 0.2 between the plate and the object,
    what is the work done agaisnt the friciton and the gravity?

    I think i found the work against the frictions which is wrong and NOT the answer at the behind of book
    80N*Sin 30 =40N <<is the force on the inclined plate of the 80N object
    so the Friction is 0.2*40 =8N

    so work against the friction is 25*8 =200N which is wrong
    what is da correct answer

    work agianst the Gravity is:
    sin 30*25 =12.5 m which is vertical distance traveled.
    so Work=F*D =80N*12.5m = 1000
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member bugatti79's Avatar
    Joined
    Jul 2010
    Posts
    461
    Quote Originally Posted by silvercats View Post
    8kg object is dragged 25m distance on a 30 degrees
    inclined plate.if the friction coefficient is 0.2 between the plate and the object,
    what is the work done agaisnt the friciton and the gravity?

    I think i found the work against the frictions which is wrong and NOT the answer at the behind of book
    80N*Sin 30 =40N <<is the force on the inclined plate of the 80N object
    so the Friction is 0.2*40 =8N

    so work against the friction is 25*8 =200N which is wrong
    what is da correct answer

    work agianst the Gravity is:
    sin 30*25 =12.5 m which is vertical distance traveled.
    so Work=F*D =80N*12.5m = 1000
    The force required to drag the object up the plane is a combination of the friction force and the force due to gravity.
    The friction force is F=u*n where n is the normal force acting perpendicular to the inclined plane and is
    F1=0.2*8*9.81*cos 30 = 13.593N

    The force due to gravity is F2=w*sin 30 = 39.24N

    Total force is F1+F2=52.833N

    Work done is W=F*d=52.833N*25m=1321Nm
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member silvercats's Avatar
    Joined
    Mar 2011
    Posts
    67
    Quote Originally Posted by bugatti79 View Post
    The force required to drag the object up the plane is a combination of the friction force and the force due to gravity.
    The friction force is F=u*n where n is the normal force acting perpendicular to the inclined plane and is
    F1=0.2*8*9.81*cos 30 = 13.593N

    The force due to gravity is F2=w*sin 30 = 39.24N

    Total force is F1+F2=52.833N

    Work done is W=F*d=52.833N*25m=1321Nm
    but book says work against the gravity is 346.4j
    and work against the gravity is 1000j :-O
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    May 2011
    Posts
    34
    maybe they are in another planet or something
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member silvercats's Avatar
    Joined
    Mar 2011
    Posts
    67
    haha funny....But NOT in this planet .
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,623
    Thanks
    428
    8kg object is dragged 25m distance on a 30 degrees
    inclined plate.if the friction coefficient is 0.2 between the plate and the object,
    what is the work done agaisnt the friciton and the gravity?
    using 10 for g ...

    work done by gravity = -(mgh) = -8g(12.5) = -1000 \, J

    work done by friction = -(0.2)8g\cos(30) \cdot 25 = -346.4 \, J

    but book says work against the gravity is 346.4j
    and work against the gravity is 1000j :-O
    I think you meant work against friction first ...
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Junior Member silvercats's Avatar
    Joined
    Mar 2011
    Posts
    67
    from where did that .25 come from?(Nice signature "... work smart, not hard.")
    Last edited by silvercats; May 27th 2011 at 05:48 PM.
    Follow Math Help Forum on Facebook and Google+

  8. #8
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,623
    Thanks
    428
    Quote Originally Posted by silvercats View Post
    from where did that .25 come from?
    what 0.25 ? there's a whole number 25 for the displacement ...
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Junior Member silvercats's Avatar
    Joined
    Mar 2011
    Posts
    67
    ahh yeah.I was confused.sorry.I use * for multiplication than . . .Thanks for the help!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Car on an inclined plane
    Posted in the Advanced Applied Math Forum
    Replies: 0
    Last Post: March 21st 2009, 05:47 PM
  2. Inclined Plane Problem
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: May 7th 2008, 06:57 PM
  3. Probability Problem - worms on a plate
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: March 31st 2008, 07:19 PM
  4. Inclined plane
    Posted in the Math Topics Forum
    Replies: 3
    Last Post: February 20th 2008, 01:10 AM
  5. for PH and others so inclined
    Posted in the Number Theory Forum
    Replies: 3
    Last Post: December 23rd 2006, 12:54 AM

/mathhelpforum @mathhelpforum