A newly discovered planet named Astra has a mass of and a radius of

PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

A newly discovered planet named Astra has a mass of 5.0×1024 kg5.0\times10^{24}\,\text{kg} and a radius of 5.0×106 m5.0\times10^{6}\,\text{m}. A student standing on a platform 50 m50\,\text{m} above Astra’s surface drops a stone from rest. (i) Using the universal gravitational constant G=6.67×10−11 N m2 ⁣/kg2G = 6.67\times10^{-11}\,\text{N\,m}^2\!/\text{kg}^2, calculate the acceleration due to gravity at the surface of Astra. (ii) Determine the time taken by the stone to reach the surface of Astra. (iii) Find the weight of a 2 kg2\,\text{kg} object on Astra and compare it with its weight on Earth (gEarth=9.8 m/s2)(g_{\text{Earth}} = 9.8\,\text{m/s}^2).

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