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Q & A: Kicking a ball barefooted on a space station

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Most recent answer: 12/24/2012
Q:
A barefoot astronaut kicks a ball, hard, across a space station. Does the ball's apparent weightlessness mean the astronaut's toes don't hurt? Explain.
- D.V. SATHISH (age 48)
mysore karnataka India
A:
Ouch!  Don't do it either on the ground or in a weightless environment. It will still hurt even on a space station.  The basic physics principle here is the difference between weight and mass.   Weight is the force on an object of mass m due to the earth's gravitational attraction. This force is equal to mg where g is the acceleration due to the earth's gravity. When you kick a football or accelerate any object, there will be a force given by F = ma where  m is the mass and a is the instantaneous acceleration.
By the way, the earth still attracts a football even when it is orbit.  The football still accelerates towards the center of the earth but since the space station is circling the earth there is always an component of acceleration in a radial direction that makes the apparent weight equal to zero.  

LeeH

(published on 12/24/2012)

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