The bicyclist accelerates with magnitude a such that
25.0 m = 1/2 a (4.90 s)²
Solve for a :
a = (25.0 m) / (1/2 (4.90 s)²) ≈ 2.08 m/s²
Then her final speed is v such that
v ² - 0² = 2a (25.0 m)
Solve for v :
v = √(2 (2.08 m/s²) / (25.0 m)) ≈ 10.2 m/s
Convert to mph. If you know that 1 m ≈ 3.28 ft, then
(10.2 m/s) • (3.28 ft/m) • (1/5280 mi/ft) • (3600 s/h) ≈ 22.8 mi/h
