How to Calculate Initial Speed

The speed of an object, such as a car or baseball, measures how quickly it traverses a given distance in a given amount of time. Feet per second is a common unit for measuring speed. Initial speed refers to the object's speed at the start of a time interval, while final speed is its speed at the end of the time interval. Acceleration determines how much the initial speed and final speed differ. For example, a car may accelerate to speed up or decelerate to slow down. A deceleration is an acceleration working opposite the direction of motion.

• 1

  Convert the time elapsed into seconds. This is accomplished by multiplying 60 if given time in minutes or multiplying by 3,600 if given time in hours. For example, a time of 2.3 minutes corresponds to 138.0 seconds (2.3 x 60 = 138).

• 2

  Multiply the acceleration of the object by the time that passed during its motion. Call this quantity "x." Assume as acceleration of 10.0 feet per second squared for the illustration exercise. Now you have 10.0 feet per second squared times 138.0 seconds, which equals 1,380.0 feet per second (10 x 138 = 1,380).

• 3

  Subtract "x" from the final speed of the object to obtain initial speed in feet per second. Use 2,100.0 feet per second for the sample exercise. In this case, 2,100.0 feet per second minus 1,380.0 feet per second equals an initial speed of 720.0.