1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: A monkey falls from a tree problem

  1. Sep 30, 2012 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations

    x= x.initial + v.initial(t) + .5(a)t^2

    v= v.initial + at

    v^2= v.initial^2 + 2ad

    3. The attempt at a solution
    I tried plugging into above formulas but there were too many unknowns.
    I'm not sure what I'm missing. Please help, I'm sure this is a simple question.
    Also, only kinematics allowed, not potential energy.
  2. jcsd
  3. Sep 30, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The angle theta can be determined from the givens. Both the dart and monkey fall at the same rate downward. Better get the monkey before it hits the ground at what time?
  4. Sep 30, 2012 #3
    I don't know how to get the time
  5. Sep 30, 2012 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    How long does it take the monkey to hit the ground? Use one of the kinematic equations knowing the vertical distance and the downward acceleration of the monkey. You listed it already.
  6. Sep 30, 2012 #5
    ok thanks
  7. Sep 30, 2012 #6
    also what should my displacement be. should i use -10-0 or something to do with y. I am confused on that part
  8. Sep 30, 2012 #7
    ok i got the time. but i don't know how to find vertical velocity because i don't know what to use for displacement of dart.
  9. Sep 30, 2012 #8
    what do h and y have to do with the question
  10. Sep 30, 2012 #9
    There 3 motions here.
    1. the dart travelling horizontally.
    2. the dart travelling vertically
    3. monkey travelled vertically.

    It means the monkey and dart are at same location after travelling at same time when they meet.

    Let the time=t
    Let the point of meeting at coordinate x,y.
  11. Sep 30, 2012 #10
    is the answer 33.725 m/s. I used -1.2 meters for displacement because the question wanted minimum velocity and that meant when the monkey hit the ground, the dart would hit him, right? And from the diagram, we see the gun is 1.2 meters above ground by 11.2-10. Is this right?
  12. Sep 30, 2012 #11
    Write all the equations for 3 motions I've mentioned and we will check if they need any corrections.

    Let the initial velocity = v, angle=θ
    Last edited: Sep 30, 2012
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook