The impact between a bat and a baseball lasts just around 1/1000 of a second. The "muzzle velocity" of a thrown baseball decreases by around 1 mph every 7 feet after it leaves the pitcher's hand, which is good news for batters. By the time it reaches the plate, it has lost around 8 mph. A batter can estimate how fast it was traveling by measuring how far it went - the farther it travels, the faster it goes. When a ball is hit up the middle, it is about as likely to continue straight ahead as it is to turn toward right field. If it does curve, it usually bends to left field. This is because the center-field fence is closer to home plate than the fences in either direction, so a ball that stays in the middle will be hard to reach with an outstretched arm. A ball that rolls away from the hitter is often called a "groundout". That is what happens if a ball is not hit up the middle but instead hits the ground first. Sometimes this happens because the batter makes some kind of error (such as swinging at a pitch outside the strike zone) or because the pitcher misses his spot and throws the ball low and inside. When this happens, the batter should wait until the ball is put into play before he decides where to go.