Question

If there was a hole through the earth would you be stopped in the middle due to gravity or would you fall straight through?
Asked by: Kirk Herren, 10 years old

All objects are attracted to the centre of the Earth.

If the hole runs through the centre it will be rather like pulling a pendulum to one side and allowing it to settle, the pendulum oscillating back and forth. Thus you would fall in a straight line accelerating towards the centre then deccelerating away from the centre until you, almost reach the other side of the earth and your velocity is zero. Then you will be drawn back, accelerating and deccelerating again, to almost where you originally fell. Each journey back and forth like the pendulum gets shorter and shorter until you settle stationery at the centre of the earth. This is due to the fact that there is air in the hole which provides friction or drag. Such motion is called Damped Harmonic Motion (if the hole was in vacuum then your would not settle at the centre but would continue to execute a full simple harmonic motion)

Holes not going through the centre have similar effects but you would fall in a curve and bump the side of the hole half way down, as the earth trys to attract you to its centre. You will again end up half way down the hole but stuck to the side which is closest to the earth's centre.
Answered by: Don Bird, Berkshire UK

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