A-level Physics (Advancing Physics)/Gravitational Fields/Worked Solutions

G = 6.67 x 10−11 m3kg−1s−2 1. A 15 kg object has a weight of 8000N. What is the gravitational field strength at this point? 2. Draw a graph of gravitational field strength against distance. Image:Grav_field_sphere.svg Since gravitational field strength is proportional to gravitational force, the two graphs look very similar. 3. What is the gravitational field strength of the Sun (mass 2 x 1030kg) on the Earth (mass 6 x 1024kg, mean orbital radius 15 x 1010m)? 4. What is the difference in the acceleration due to gravity over a vertical distance d? 5. How far would one have to travel upwards from the Earth's surface to notice a 1Nkg−1 difference in gravitational field? (The Earth has a radius of 6400 km.) Using the quadratic formula: Which is very horrible. If you plug in the numbers, you get: Since we want a negative d (because of the minus sign we ignored right at the beginning): Although, I have to confess, there was so much scope for error that it is almost certain that this is the wrong answer. If you fancy wading through and checking, feel free! [*] Solution : g'=g-1=9.8-1=8.8N/kg g=GM/(R+d)^2 => d=349.96 km --Sjlegg (talk) 14:18, 23 April 2009 (UTC)