Finding change in kineic energy?

Question

a 5.9 Kg particle moves along the x axis under the influence of a single conservative force. if the work done on the particle is 85J as it moves from x1 =1.2 m to x2 = 5.2 m, find the change in its kinetic energy. answer in J?

Answer 1

Work = Force * distance

85 / 4 = Force = 21.25 Newtons

Force = m * a

21.25 / 5.9 = a = 3.60 m/s^2

V^2 = Vo^2 + 2a(x - x0)

Vo^2 = 0

V^2 = 2a(4) = 8a

Energy = 0.5 * m * V^2

= 0.5 * m * 8a

= 0.5 * 5.9 * 8(3.60)

= 85 Joules -- same as the added work

V = squareroot(8*3.6) = 5.36 m/s

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