re: HSC Physics Marathon Archive
Mount Everest is the worlds tallest mountain, however, it is not the point on the Earths surface at which acceleration due to gravity is the lowest. Explain.
Gravitational field strength is given by the formula g = GM/r^2. Although we may expect it to have the lowest value of g, since g decreases with the radius (and hence altitude) we are above the earth's surface, there are many reasons why Mt Everest may not have the lowest gravitational field strength.
1. the earth under and on Mt Everest may be more dense than other parts of the earth, which would mean that there is a greater localised mass near Mt Everest. By the equation given above, that would increase the value of g at Mt Everest
2. Mt Everest is located between the equator and the poles. Because of the ellipsoid shape of the earth, the earth has a larger radius at the equator. This means that a mountain at the equator may have a lower value of g.
3. Further, the axial rotation of the earth creates a pseudo centrifugal force that acts outwards from the centre of the earth, reducing the value of g. Because the axial rotation is most prominent at the centre, so is this effect. Mt Everest is not very close to the equator, and hence its value of g is not greatly impacted by this effect. Rather, a mountain or high land feature at the equator would be.
Therefore, because of the above factors, Mt Everest understandably does not have the lowest acceleration due to g. Rather, it would be expected that a high land feature or mountain at the equator MAY have the lowest value of g.