At lift–off a rocket (including fuel) has mass

PHYSICS · Subjective · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

At lift–off a rocket (including fuel) has mass 2.0×104 kg2.0\times10^{4}\,\text{kg}. After reaching an altitude of 300 km300\,\text{km} its mass has decreased to 1.5×104 kg1.5\times10^{4}\,\text{kg} owing to fuel consumption. Neglect Earth’s rotation and take RE=6400 kmR_{\rm E}=6400\,\text{km} and g=9.8 m s−2g=9.8\,\text{m\,s}^{-2} at the surface. (a) Determine the acceleration due to gravity at 300 km300\,\text{km} altitude. (b) Calculate the weight of the rocket at lift–off. (c) Calculate the weight of the rocket at the stated altitude. (d) Find separately (i) the percentage decrease in weight due only to change in altitude and (ii) the percentage decrease due only to reduction in mass.

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