Answer to Question #181139 in Physics for Andu

Question #181139

5. The body, weighing 4kg, rises at a constant speed v = 2 m / s, under the action of a constant force F. Find the force of force F, as well as the work performed by it during 2s.


1
Expert's answer
2021-04-19T17:08:47-0400

Since the speed of the body is constant, the force FF should be equal and opposite to the weight of the body. Thus:


F=mgF = mg

where m=4kgm = 4kg is the mass of the body, and g=9.8m/s2g = 9.8m/s^2 is the gravitational acceleration.

The power of this force is then:


P=Fv=mgvP = Fv = mgv

where v=2m/sv = 2m/s is the speed of the body.

And the work is:


W=Pt=mgvtW = Pt = mgvt

where t=2st = 2s is the time. Thus, obtain:


P=49.82=78.4WP = 4\cdot 9.8\cdot 2 = 78.4WW=49.822157JW = 4\cdot 9.8\cdot 2\cdot 2 \approx 157J

Answer. Power: 78.4W, Work: 157J.


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