What is the force exerted by the tire on the stone? [closed]

A stone with mass $m$ gets stuck in the tire of a car, whose radius is $r$. The car is moving at constant speed $v$.

The problem asks to determine the force $F$ exerted by the tire on the stone, when this is at maximum distance from the ground. Now, I know the centripetal force is $F_1=\dfrac{mv^2}{r}.$ Why is it that in the solution the weight of the stone is subtracted from $F_1$ to get $F$, rather than added? I mean, they're both downward.

closed as off-topic by AccidentalFourierTransform, stafusa, Chris♦, glS, Jon CusterFeb 19 '18 at 16:09

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – AccidentalFourierTransform, stafusa, Chris, glS, Jon Custer
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Remember that $F_{net}$ is the sum of all the forces.