The radius of the circular motion at the given speed is 1.56 m.
The given parameters;
The radius of the circular motion is calculated by using centripetal acceleration formula as follows;
[tex]a_c = \frac{v^2}{r} \\\\r = \frac{v^2}{a_c} \\\\r = \frac{2.5^2}{4} \\\\r = 1.56 \ m[/tex]
Thus, the radius of the circular motion at the given speed is 1.56 m.
Learn more about centripetal acceleration here: https://brainly.com/question/79801