1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Physics homework =d

  1. Jan 18, 2010 #1
    1. The problem statement, all variables and given/known data
    Assume gravitational force is 9.8 ms^-2

    In a local bar, a customer slides an empty beer mug on the counter for a refill.
    The bartender is momentarily distracted and does not see the mug, which
    slides off the counter and strikes the floor 1.4 m from the base of the counter.
    If the height of the counter is 0.86 m,

    (a) with what velocity did the mug leave the counter, and
    (b) what was the direction of the mug’s velocity just before it hit floor?

    2. The attempt at a solution

    Don't really understand the question at all =d can any1 help =D

    Ans (a) 3.34 m/s at 0° (b) 309°
  2. jcsd
  3. Jan 18, 2010 #2


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    Try determining the time that it takes for an object to fall from .86m.
  4. Jan 18, 2010 #3
    the first thing u should do when doing a problem like this is split it up into a problem in the x (horizontal)direction, and one in the y (vertical)direction. Try to view it as two separate problems but with one common factor that will always stay the same between the two problems. Split up different distances, acceleration, and different velocities and other relevant information. Once done with that you might have some more insight on how the problem is handled.
  5. Jan 18, 2010 #4
    lol thx for the all help appreciate it =D i got the answer i guess
    => s = ut + 1/2at^2 ( vertical distance )
    => u = 0, sqrt(2s/a) = t
    => t = 0.41893938

    => s = 1/2(u+v)t ( horizontal distance )
    => 1.4 = 1/2(u + v) t where v = u
    => 1.4/t = 1/2 * 2u
    => u = 3.341772263
    Last edited: Jan 18, 2010
  6. Jan 18, 2010 #5
    the next part really stumps me =o
    how do you calculate rotation angle
    does it have something to do with projectile motion thing
    ill go try out
  7. Jan 18, 2010 #6


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    You know the velocity of the glass in the X-direction. If you can determine the velocity in the Y-direction at impact, you can determine the angle.
  8. Jan 18, 2010 #7
    is the velocity in Y-direction
    => v^2 = u^2 + 2as
    => v = sqrt(2as)
    => v = sqrt(2*9.8*0.86)
    => v = 4.105605924
    => v = 4.11m/s

    how do u find the angle =o

    i can only think of tan(teetle) = vertical v / horizontal v which is wrong
    nvm i forgot to do 360-teetle lol =D
    thanks everyone for helping me to solve this question =D
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook