1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A question on units

  1. Oct 13, 2007 #1
    I *think* this is right, but if there is something obviously wrong please tell me where


    Ive got a mass of weight 'y' dropped onto a surface that can support 10y
    there is no wind resistance
    the mass starts from stationary and accelerates under gravity (assumed to be 9.8 m/s/s)
    the distance is 3m

    constant acceleration from stationary for s distance is v^2=2as. v^2=2(9.8)3=7.6 m/s
    The kinetic energy of a particle of mass m moving at velocity v is 1/2*m*v^2 K=1/2(y)(7.6^2)=29.4y

    so the particle would excede the resistance by 19.4y

    with respects to the different units involved is this correct, or can i not take the resistance of the surface (measured in neutons) away from the kinetic energy of the particle (measured in joules) to get an answer because of the different units?
     
  2. jcsd
  3. Oct 13, 2007 #2

    Astronuc

    User Avatar

    Staff: Mentor

    The relationship between mass m and weight y is m = y/g.

    Energy/work is equated to force * distance, so 1 Joule (J) = 1 Newton * 1 m = 1 N-m.


    Force accelerates/decelerates a mass.

    It would seem one needs to determine the deflection of the surface or the time needed to decelerate the mass y/g in order to determine the force.

    http://hyperphysics.phy-astr.gsu.edu/hbase/impulse.html
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: A question on units
  1. Units Question (Replies: 3)

  2. Units question (Replies: 4)

  3. Units question (Replies: 21)

  4. Units Question (Replies: 2)

  5. A question on units. (Replies: 1)

Loading...