Problems with Power only using velocity and force

AI Thread Summary
The discussion revolves around calculating the power of an object influenced by a force, using the formula Power = F * v. Initial calculations yielded various power values based on the components of velocity and force, but confusion arose regarding the treatment of negative velocity and the nature of power as a scalar quantity. It was clarified that power is not a vector, and thus the components should not be squared and added to find a magnitude. Instead, the correct approach is to directly multiply the force and velocity components, leading to a final power calculation of -5W. The conclusion emphasizes understanding the scalar nature of power in physics.
Psip
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Homework Statement


An object moving with a velocity whose components are [4m/s,-1m/s,3m/s] is acted on by a force whose components are [-5N,0,+5N]. What is the power of the energy transfer involved in this interaction?

Homework Equations


Power=F*v

The Attempt at a Solution


4m/s*-5N= -20W
-1m/s*0=0W
23m/s*5N=15W

(202+152+02)sqrt=Magnitude = 25W which could be the answer but I'm not sure. I just don't know how negative velocity affects power because P=Fv so if F is 5N and v=-3m/s then it would seem like -15W is the answer but I am not sure. I also don't really have experience with 3-component vectors.
 
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It's OK up to here.

Psip said:
(20^2+15^2+0^2)sqrt=Magnitude = 25W

This treats the three amounts you have calculated as vectors, but they are not. Power is not a vector. So you don't square and add to get a magnitude. You just add.

Power is the scalar product (dot product) of force and velocity.
 
Thank you for your reply, that does make sense that Power isn't applied in a direction. So the answer is -5W
 

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