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Why is the friction force not in the negative direction?

Hi devon.gibson2016, yes, it's typical that friction is often in the negative direction since kinetic friction, such as air friction, is often what's slows things down. In this case air friction would be in the opposite direction to the direction of motion, and positive would be taken as the direction of motion, making friction pointing in the negative direction. In this particular question, however, the friction we're speaking of is causing the motion. In this question we're dealing with static friction, which is the friction force exerted on the drag racer tires by the road. The drag racer tires push backwards on the road, and the road in turn pushes forward on the tires. This forward static friction force is the Newton's 3rd law counterpart to the force exerted backward on the road by the tires. This static friction force is in the same direction as the positive direction of motion, so it's positive.

All the best,
Mr. Dychko