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: Physics Motion Problem (Displacement)

  1. Mar 6, 2008 #1
    1. Hi, my question deals with displacement and given acceleration : A boy and a ball are at the top of a ramp. the ball rolls down accelerating at 0.2 m/s(squared). The boy chases after the ball 12 seconds later accelerating at 0.9 m/s(squared). The length of the ramp is 60 meters. Will the boy catch the catch the ball before the end of the ramp, if so what displacement/ time will it be at

    2. I was trying to use v2=v1 + aΔt, and manipulate it for the getting the time by after using the equation, Δd=v1Δt+0.5a(Δt)squared

    3. My attempt was by trying to divide the displacement by the acceleration and i think i got time(squared) so i square rooted that and than i plugged in the that time by the acceleration to get velocity at that time, and than calculating the displacement by multiplying the velocity by the time. I also tried to substitute the time/ displacement values into each other but i could not balance it out to solve it algebraically. I also tried graphing it and i got my answer somewhere around 15 seconds but i'm not allowed to graph

    Any Help would be appreciated.... Thanks
  2. jcsd
  3. Mar 6, 2008 #2
    the total length of ramp = 60 m
    So, s= 1/2(0.2)t^2 =0.1t^2
    after 12s s' = (0.1)(12)^2=14.4 m
    for the motion of boy
    combine the equation, find t
    if 14.4+(0.1)t^2>=60 it is impossible
    <=60 , it is possible
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook