## To solve this problem, we can use the concept of rotational acceleration and the formula for rotational speed. The given information tells us that the rotational speed at the end of the first minute is 0.90 (or 90%) of the initial rotational speed.

Here's how you can handle it step by step:

1. Write down the given information:

- Initial rotational speed (ω₀) = 250 rev/min

- Rotational speed at the end of the first minute (ω₁) = 0.90 * 250 rev/min

2. Multiply the initial rotational speed by 0.90 to find the rotational speed at the end of the first minute:

ω₁ = 0.90 * 250 rev/min

ω₁ = 225 rev/min

Therefore, the rotational speed at the end of the first minute is 225 rev/min.