Although we may not think about it, the roads on which we drive are an application of physics. When they have to calculate the maximum degree until which a curve is safe for a car to make, engineers need to consider friction. Friction is defined as the resistance that one surface or object encounters when moving over another. It is what allows people to walk forward and cars to drive onward; without it, we would all remain in the same place, regardless of how much we tried to move. Engineers also use this concept when deciding on a safe maximum speed at which cars should drive (speed limit).
