Escape Speed (2/2)
Here's the calculation for how fast an object has to go to escape earth.
Note we have both kinetic and potential energy at the beginning. The reason both are zero at the end is because of reference frame. We called the potential energy at a point so far away that the force of gravity is near zero our zero point. Hence U final is zero.
The reason we set K final as zero is that we're looking for a minimum speed to escape. An object in this situation would get really far away with its last breath of speed and then stop and sit there. Any object moving faster than this original velocity would get far away and keep moving. We call this minimum speed "escape speed."
Escape Speed (2/2)
Here's the calculation for how fast an object has to go to escape earth.
Note we have both kinetic and potential energy at the beginning. The reason both are zero at the end is because of reference frame. We called the potential energy at a point so far away that the force of gravity is near zero our zero point. Hence U final is zero.
The reason we set K final as zero is that we're looking for a minimum speed to escape. An object in this situation would get really far away with its last breath of speed and then stop and sit there. Any object moving faster than this original velocity would get far away and keep moving. We call this minimum speed "escape speed."