A particle of mass 5kg is acted upon by a force of 400N for a distance of 20m along the x axis. What is its final velocity if it is initally at rest?

The work done by a force on a particle is: Work done = Force x Displacement.The energy of a particle is given by the sum of its potential and kinetic energies.As the particle does not gain or lose any height (in the y axis), only its kinetic energy changes.Therrfore the work done by the force is 400(N) x 20(m) = 8000(J).This is equal to its change in kinetic energy = 0.5 x m x v² . = 0.5 x 5 x v².By algebra: sqrt(2x8000/5) = v = 56.6ms^-1.