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: Work done by tension force

  1. Apr 9, 2005 #1
    here's the question:
    a mass of 100kg is pulled directly upward a distance of 5m by a rope with acceleration 1m/s^2. what is the work done by the tension force?

    so the normal force is mg, 100kg*10m/s^2(gravitational constant given)= 1000N
    the applied force is 100kg*1m/s^2= 100N
    so is the tension 1000+100? if so the work done is 1100N*5m= 5500J
    it's being pulled straight up, so the angle is 0, cos0=1

    is it correct to add the two forces to find the total tension?
     
  2. jcsd
  3. Apr 9, 2005 #2

    quasar987

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    <quasar go hide in the corner>
     
    Last edited: Apr 9, 2005
  4. Apr 9, 2005 #3

    xanthym

    User Avatar
    Science Advisor

    SOLUTION HINTS:
    From problem statement:
    {Mass of Object} = m = (100 kg)
    {Gravitational Force Downward on Object} = m*g = (100 kg)*(9.81 m/sec^2) = (981 N)
    {Acceleration of Object Upwards} = a = (1 m/sec^2)
    {Distance Object Pulled Upwards} = H = (5 m)
    {Rope Tension Force Upward} = T

    {NET Total Force on Object Upward} = m*a =
    = {Rope Tension Force Upwards} - {Gravitational Force Downward} =
    = T - m*g
    ::: ⇒ m*a = T - m*g
    ::: ⇒ T = m*a + m*g

    {Work Done By Rope Tension} =
    = {Rope Tension Force Upward}*{Distance Object Pulled Upwards} =
    = T*H =
    = {m*a + m*g}*H

    ::: ⇒ {Work Done By Rope Tension} = {m*a + m*g}*H
    Evaluate above equation to determine work performed by Rope Tension.


    ~~
     
    Last edited: Apr 9, 2005
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook