Final answer:
To calculate Elizabeth's speed, you divide the distance traveled by the time it took. She moves 2 meters in 8 seconds, giving a speed of 0.25 meters per second. The equation for Elizabeth's progress, considering her constant speed, is x = 0.25t + 11.
Step-by-step explanation:
The question involves calculating Elizabeth's speed over a specific time during a race, and then writing the equation to represent her progress. Elizabeth is at 11 meters after 4 seconds, and at 13 meters after 12 seconds. First, we must determine her speed. Speed is distance divided by time. So, from 4 to 12 seconds, which is 8 seconds, Elizabeth travels 2 meters (13 meters - 11 meters). Thus, her speed during this time is 2 meters divided by 8 seconds, which equals 0.25 meters per second.
To write the equation of her progress, we can use the formula for uniform motion, which is distance = speed x time. Since her speed is constant at 0.25 meters per second, the equation for her progress x in t seconds would be x = 0.25t + 11, where we add 11 to account for the initial 11 meters she covered in the first 4 seconds.