When can a car have no acceleration but still be moving?

question 6 options:

when the car is moving at a constant velocity

when the car is still moving but coming to a stop

when the car starts at 0m/s and speeds up to 15m/s

when the care is moving at a constant velocity, it have zero acceleration.

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