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## Homework Statement

An object weighting 100N is traveling vertically upward from the earth in the absence of air resistance at a constant velocity of 5 m/s. What is the power required to keep the object in motion?

## Homework Equations

P = ΔE/t and P = Fvcosθ

## The Attempt at a Solution

The explanation given in TPR(the princeton review book) is: since the object's velocity is upward and constant and the force necessary to propel the object is also upward and constant we may use the equation: P = Fv = 100N(5) = 500W.

What I don't understand is this: If the velocity is constant, then the force should be zero, and that should make the Power zero too, right?