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!

>Laws of Motion Problem <

  1. Jan 5, 2008 #1
    1. The problem statement, all variables and given/known data

    An insect crawls very slowly on a hemi-spherical shell..
    The coeff. of friction between insect and surface of sphere is 1/3.
    The line joining the centre of the shell to the insect makes an angle of @ with the vertical.



    Help will be higly appreciated>><<
  2. jcsd
  3. Jan 5, 2008 #2


    User Avatar
    Homework Helper

    The thing to consider is this. What angle would a flat surface make to the horizontal before an object on it would just start to slip, if the coefficient of friction between that object and the surface were
    1/3? Now consider a small flat surface that is tangent to the surface of the hemisphere. Where on the shell would the tilt of that surface to the horizontal have that value you found? For the imaginary line from the center of the shell to that tangent point on the shell's surface, what angle to the vertical does that line make? (A little drawing would be helpful here.)
  4. Jan 5, 2008 #3
    Sir i think the concept to be used here is the same as that of angle of repose in an inclined plane.....i.e. the maximum value of inclination that prevents the object to slip...

    am i correct with the thought application???
  5. Jan 5, 2008 #4
    thanks a lot sir...

    your concept of placing a horizontal plane was really helpful...

    i assumed the plane to be a banked road for the insect..and then since the ques says that the insect moves very slowly..then i am sure it does not possess the max velocity..
    for a car on a banked rd and whose v is less than v[max]..the car can be parked only if
    tan@<=coeff. of friction.
    similarly the case with insect on the hemispherical shell...

    applying the rule,,we get...

    solving we get..cot@<=3

    hence max angle is defined by....cot@=3.

  6. Jan 5, 2008 #5


    User Avatar
    Homework Helper

    A velocity is not really important to the problem. As with the car on the banked road, the issue is with the amount of static friction. The insect would not even be able to stay in place if it were further down on the shell.

    I agree. :-) (The angle that the imaginary tangent plane makes to the horizontal is the same as the angle the line from the center of the shell to the tangent point makes with the vertical.)
    Last edited: Jan 5, 2008
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: >Laws of Motion Problem <
  1. Laws of motion Problem (Replies: 2)

  2. Laws of Motion Problem (Replies: 2)

  3. Laws of motion problem (Replies: 7)