Why are almost all satellites launched from west to east? Estimate the velocities that must be communicated to a satellite to be launched into a low circular orbit along the equator, west to east and east to west.
Decision:
Because of the daily rotation of the Earth, all points on its surface have some velocities pointing from west to east. Points along the equator move at a velocity $v = \frac{2 \pi R_{earth}}{T}$, where $T = 1 \:day$ is the Earth's rotation period. Calculating this velocity, we get $v \approx 0.5 km/s$. Therefore, the velocity that would be required to launch the satellite in the western direction is 1 km/s more than the speed needed to launch it in the eastern direction.
Decision:
Because of the daily rotation of the Earth, all points on its surface have some velocities pointing from west to east. Points along the equator move at a velocity $v = \frac{2 \pi R_{earth}}{T}$, where $T = 1 \:day$ is the Earth's rotation period. Calculating this velocity, we get $v \approx 0.5 km/s$. Therefore, the velocity that would be required to launch the satellite in the western direction is 1 km/s more than the speed needed to launch it in the eastern direction.