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: F=MA Exam 2010 Question 10

  1. Jan 17, 2013 #1
    1. The problem statement, all variables and given/known data
    A block of mass m1 is on top of a block of mass m2. The lower block is on a horizontal surface, and a rope can pull horizontally on the lower block. The coefficient of kinetic friction for all surfaces is μ. What is the resulting acceleration of the lower block if a force F is applied to the rope? Assume that F is sufficiently large so that the top block slips on the lower block.

    2. Relevant equations

    F = ma
    Frictional Force = Normal Force * μ

    3. The attempt at a solution

    Normal Force (for lower block) = (m1 + m2) g
    Frictional Force (for lower block) = μ * (m1 + m2) g
    F - (μ * (m1 + m2) g) = m2 * a
    a = ((F - (μ * (m1 + m2) g)) / m2

    Correct Answer should be: a2 = (F - μg(2m1 + m2)) / m2
  2. jcsd
  3. Jan 17, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper

    welcome to pf!

    hi vjnmath! welcome to pf! :smile:
    … sooo, you'll need to include the friction force from the top block :wink:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook