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Block movement - dynamics

  1. Mar 19, 2012 #1
    1. The problem statement, all variables and given/known data
    Hi guys. First of all, great forum you've got here.

    I have a problem and I hope you can help me with this one.

    Block of mass m lies on a rough horizontal surface. In the period 0 - t1, the block is moving due to the force F(t), which varies depending on the time. In period t1 - t2 we only have friction (F=0), and the block in the time t2 has speed v2=1 m/s. I have to find time t2, acceleration in t2 (a2) and distance s2. I also have to draw a, v, t diagrams.

    2. Relevant equations

    m2v⃗ -m1v⃗ 1=∫F(t)⃗ dt


    3. The attempt at a solution

    9q9w6b.jpg

    my formula in mathcad

    uvvx3.jpg

    I'm stuck with this integration. I understand that the first part (F*cos(60°)) is the area under the curve - √2 *m*g

    I hope you guys can help. Thank you in advance.
     
  2. jcsd
  3. Mar 19, 2012 #2
    wow, 400 views and no reply lol

    I was quite busy today but I tried a different approach.
    First, I only calculated the part from 0 to t1 with that Impulse formula and the speed v1 (@ t1) is 4.346 m/s.

    Then, since the force is F=0, I have Fn=m*g (y axis), and Frx=-μ*m*g (x axis).
    And when I try to calculate this part, I get a weird result -> t2=0.394 s lol.
    IDK, this could only make sense if the real t2 time would be √2+0.394=1.808 seconds

    :blushing:
     
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