A runner dashes from the starting line (x = 0) to a point 108 m away and then turns around and runs to a point 18 m away from the starting point in 21 seconds. To the nearest tenth of a m/s what is the average speed?
Find the total distance the runner travels.
- the runner runs 108m
- the runner turns around and runs 108 - 18 = 90m
Find the total time.
- the runner runs the distance in 21s
So the average speed is the total distance over the total time.
(108m + 90m) / 21s = ?
9.43m/s
To find the average speed, we need to divide the total distance traveled by the total time taken. In this case, the runner runs from the starting line to a point 108 m away, and then turns around and runs to a point 18 m away from the starting point.
The total distance traveled by the runner is the sum of the distance covered in the first part (starting line to 108 m away) and the distance covered in the second part (108 m away to 18 m away from the starting point).
First, let's find the distance covered in the first part. The runner starts at x = 0 and reaches a point 108 m away, so the distance covered in the first part is 108 m.
Next, let's find the distance covered in the second part. The runner starts at the point 108 m away and reaches a point 18 m away from the starting point, so the distance covered in the second part is 108 m + 18 m.
Adding the distances covered in both parts, we get a total distance of 108 m + (108 m + 18 m) = 234 m.
Now, let's find the total time taken. The runner took 21 seconds to cover the entire distance.
Finally, we can calculate the average speed by dividing the total distance (234 m) by the total time (21 s):
Average Speed = Total Distance / Total Time
= 234 m / 21 s
≈ 11.1 m/s (rounded to the nearest tenth)
Therefore, the average speed of the runner to the nearest tenth of a m/s is approximately 11.1 m/s.