Question 15 $1 \mathrm{pts}$ An airplane flies in a horizontal circle of radius $400 \mathrm{~m}$ at a uniform speed of $100 \mathrm{~m} / \mathrm{s}$. What is its acceleration (in $\mathrm{m} / \mathrm{s}^{2}$ )?

Step 1 ：Given that the airplane flies in a horizontal circle of radius 400 m at a uniform speed of 100 m/s.

Step 2 ：The acceleration of an object moving in a circle of radius r at a speed v is given by the formula \(a = \frac{v^2}{r}\).

Step 3 ：Substitute the given values into the formula: \(v = 100\) m/s and \(r = 400\) m.

Step 4 ：Calculate the acceleration: \(a = \frac{(100)^2}{400} = 25.0\) m/s².

Step 5 ：Final Answer: The acceleration of the airplane is \(\boxed{25}\) m/s².