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: Finding distance using force, acceleration, time

  1. Oct 1, 2008 #1
    A dockworker applies a constant horizontal force of 89.0N to a block of ice on a smooth horizontal floor. The frictional force is negligible. The block starts from rest and moves a distance 12.5m in a time 5.10s .
    A)What is the mass of the block of ice?
    B)If the worker stops pushing at the end of 5.10s , how far does the block move in the next 5.30s ?

    2. Relevant equations: F=ma

    3. The attempt at a solution: well i was able to solve part A by using the equation
    deltaD=(v1+v2)/deltaT to find v2. and then i used a=(v2-v1)/deltaT and plugged it into F=ma to find the mass.
    For part B, i tried using the same equation for finding distance, however it could not be done cause i do not know how to find v2, and if i plug in 0 as v2, i get a wrong answer.

    so basically i need help in solving part B of this problem. thanks.
    Last edited: Oct 1, 2008
  2. jcsd
  3. Oct 1, 2008 #2


    User Avatar
    Homework Helper

    Welcome to PF.

    Don't you want to consider the relationship between x, a, and t?

    x= 1/ 2 * a * t2

    If you find a, then F = ma gives you the mass as I think you already know.

    Part b can be determined by finding the V from

    V2 = 2*a*x

    That times t gives you distance.
  4. Oct 1, 2008 #3
    you mean V^2=2 x .96 x 12.5? that gives me V=4.9, which i already had to use for part A. and if i do 4.9 x 0.2s. i get .98m, which is not the right distance
  5. Oct 1, 2008 #4
    oh wait nvm, i was reading the question wrong, i thought it was asking what the distance was after 5.3 seconds from 5.1 seconds. i didnt know it meant it was asking the distance after 5.3 MORE seconds. thanks, i got the right answer now.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook