The Earth's rotation affects its speed in a couple of ways. First, the Earth's rotation gives rise to the concept of a day, as it determines the length of time it takes for the Earth to complete one full rotation on its axis. This rotational period is approximately 24 hours.
The Earth's rotation also affects its speed in terms of its angular velocity. Angular velocity refers to the rate at which an object rotates around a fixed axis. In the case of the Earth, it rotates around its axis, and the angular velocity determines how fast it completes one full rotation.
The Earth's angular velocity is not constant throughout its rotation. Due to the conservation of angular momentum, the Earth's rotational speed decreases slightly over time. This phenomenon is caused by various factors, such as the gravitational interactions with the Moon and the Sun, the redistribution of mass within the Earth, and tidal forces.
It's important to note that the decrease in the Earth's rotational speed is extremely gradual and not noticeable within a human lifetime. The change is on the order of milliseconds over the span of a century.
In summary, the Earth's rotation affects its speed by determining the length of a day and by influencing its angular velocity, which changes over long periods of time due to various factors.