A constant force of 30 N pulls a 10 kg box to the left.  What is the velocity of the box after 5 seconds if the box was initially at rest.  (Hint – you will need to use Newton’s 2nd law and the basic acceleration equation to solve the problem).  Show me the steps and the answer please

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see attached graph

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4