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: Projectile motion questions

  1. Nov 8, 2015 #1
    Hi all. I just recently dropped psychology for physics so this topic as a whole has me stumped and the textbook isn't helping. I'll be using this thread for any questions that arise pertaining to projectile motion (so more than one), if that's cool? Should be really basic. Thanks.

    1. The problem statement, all variables and given/known data

    A salmon moving upstream to its breeding grounds jumps a waterfall 2.5m high. With what minimum speed must it leave the water below to reach the top level?

    2. Relevant equations
    Vy = Vsinθ
    Vx = Vcosθ


    3. The attempt at a solution

    Don't understand how you can work anything out with one piece of data...
    Last edited: Nov 8, 2015
  2. jcsd
  3. Nov 8, 2015 #2


    User Avatar

    Staff: Mentor

    Hi Rumplestiltskin, Welcome to Physics Forums.

    That would be contrary to forum rules. One problem per thread, so new questions get new threads (even if they are on related topics).
    You're given more than you might think as there is the assumption that this is a projectile motion problem taking place near the surface of the Earth. So you know, for example, that the motion will be affected by the acceleration due to gravity (g). and that all the standard kinematic equations for projectile motion apply.

    Some things to become familiar with in the study of projectile motion include the range formula, the launch angle for maximum range, the maximum height of a projectile given its launch conditions (speed, angle).
  4. Nov 8, 2015 #3
    After a cursory reading into the topics you mentioned I came across the vaguely familiar formula v = √2gs. Plugging in 9.81ms-2 for g and 2.5m for displacement s, I arrived at 7 ms-1 for the answer; the mark scheme confirmed this. Thanks! And sorry to waste your time.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted