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September 18, 2014

Homework Help: physics

Posted by Matt on Tuesday, March 13, 2007 at 8:41am.

A force of 8 N acts on a 2 kg object as it is displaced along the x-axis. The speed of the object when it is at x= 2m is 5 m/s.

a) what is the net work done by F(x) on the object as it is displaced from x=2m to x=8m?

sol) 8m - 2m = 6m; 6m * 8N = 48 J

b) What is the object's kinetic energy at x= 8m?

sol) Kf= Ki - W(net)
= 25J + 48 J
= 73 J (a bit too much ??)

c) what is the instantaneous power delivered by Fx when the object is at x=8m?

sol) P = F * v
= 8N * 73m/5 (?)

(a) correct
(b) E = (1/2) M V^2 + Work = 25 J + 48 = 73 J. Correct
V = sqrt(2E/m) = 8.54 m/s
(c) F*V = 8N * 8.54 m/s = 63.4 W

(Friction has been assumed negligible)

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