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Homework Help: Dynamics: Cannon ball and the moving gun

  1. Dec 9, 2016 #1
    https://postimg.org/image/z96a0jn8b/ https://postimg.org/image/z96a0jn8b/
    link to image (bcs the feature doesn't work): https://postimg.org/image/z96a0jn8b/
    1. The problem statement, all variables and given/known data

    A cannon (mass m_c) is standing on the ground before it fires a cannon ball (mass m_b). At the time t_0=0. the cannon ball is leaviing the gun at height h_m above the ground with velocity V_0 at angle alpha. Air resistance can be neglected.


    2. Relevant equations
    1. V_c(m_b,m_c,V_o,alpha)
    2. h_b(t)
    3. d(t)

    3. The attempt at a solution
    This is my attempt for question 1:
    we use F=m.a for only the horizontal direction and I got Vc=m_b.v_0.cos alpha / mc. Anyone can help me to solve the 2nd and 3rd question? I would appreciate it a lot. Thanks
    Last edited: Dec 9, 2016
  2. jcsd
  3. Dec 9, 2016 #2


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    Science Advisor
    Homework Helper
    Gold Member

    You need some latex:

    ##V_c = \frac{m_b}{m_c} v_0 \cos(\alpha)##

    Note that that is the speed of the cannon. It's clearly in the opposite direction from the ball.

    For part 2, is ##h_b(t)## the height of the ball at time ##t##?

    If so, how can you go about calculating that?
  4. Dec 9, 2016 #3


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    Staff: Mentor

    Hi rndaryam, Welcome to Physics Forums.

    The "Relevant equations" section of the template is meant for you to list any standard equations or physics laws that you feel might pertain to or otherwise be useful in solving the problem. For example, you might list the relevant projectile motion equations and the law of conservation of momentum. What you have listed is actually part of the problem statement (the things that you need to calculate).

    I've inserted a copy of your image into your post for you, so now it's visible to helpers without having to follow a link.
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