Force problem

Discussion in 'Physics' started by braddy, Oct 15, 2005.

  1. braddy

    Thread Starter Well-Known Member

    Dec 29, 2004
    I try to solve the following problem but my answer does not correspond to the solution of the textbook. Please help me to understand the problem:

    The net force acting on a particle depends on the position of the particle along the x-axis according the relation F=F0+C*x, where F0=5N and C=-2N/m. The particle is initially at rest at x=0m when the force begins to act.
    a- Calculate the work done by the force when the particle reaches x values 1,2,3and 4 m?
    b- Determine any positions ( besides x=0m ) where the work done is zero.

    I have problem for the question a.
    What I did is to compute F1=F0+C*(1) [for x=1m]
    that gives me F1=5-2=3N
    So the work for F1 is W1= F1*(1)=3J
    However the answer in the textbook it w1=4J I dont know how they get that.
    Thank you for your time.
  2. haditya

    Senior Member

    Jan 19, 2004
    the force is a function of the displacement and hence one cannot directly multiply the force iwth the displacement
    istead integrate F*dx from 0 to the final position to get the actual work done
    a similar approach can be used for part b
  3. braddy

    Thread Starter Well-Known Member

    Dec 29, 2004
    YES! thanks a lot I just tried the first value and I found the good value!