Task: Question Answering
Input (English): Context: Calculating acceleration is complicated if both speed and direction are changing or if you want to know acceleration at any given instant in time. However, its relatively easy to calculate average acceleration over a period of time when only speed is changing. Then acceleration is the change in velocity (represented by v) divided by the change in time (represented by t): acceleration = v t Look at the cyclist in the Figure 1.1. With the help of gravity, he speeds up as he goes downhill on a straight part of the trail. His velocity changes from 1 meter per second at the top of the hill to 6 meters per second by the time he reaches the bottom. If it takes him 5 seconds to reach the bottom, what is his average acceleration as he races down the hill? v t 6 m/s 1 m/s = 5s 5 m/s = 5s 1 m/s = 1s = 1 m/s2 acceleration = In words, this means that for each second the cyclist travels downhill, his velocity (in this case, his speed) increases by 1 meter per second on average. Note that the answer to this problem is expressed in m/s2 , which is the SI unit for acceleration. Q: The cyclist slows down at the end of the race. His velocity changes from 6 m/s to 2 m/s during a period of 4 seconds without any change in direction. What was his average acceleration during these 4 seconds? A: Use the equation given above for acceleration: v t 6 m/s 2 m/s = 4s 4 m/s = 4s 1 m/s = 1s = 1 m/s2 acceleration = 
 Question: the si unit for acceleration is
Output (English): m/s2.