Page 296 - Physics Coursebook 2015 (A level)

Cambridge International A Level Physics
11 Figure 18.17 shows the variation of the Earth’s gravitational field strength with distance from its centre. 10.0
8.0 6.0 4.0 2.0
00 5.0 R
Figure 18.17 For End-of-chapter Question 11.
20.0 25.0 r / 106 m
10.0 15.0
a Determine the gravitational field strength at a height equal to 2R above the Earth’s surface, where
R is the radius of the Earth. [1]
b A satellite is put into an orbit at this height. State the centripetal acceleration of the satellite. [1]
c Calculate the speed at which the satellite must travel to remain in this orbit. [2]
d i Frictional forces mean that the satellite gradually slows down after it has achieved a circular orbit.
Draw a diagram of the initial circular orbital path of the satellite, and show the resulting orbit as
frictional forces slow the satellite down. [1]
ii Suggest and explain why there is not a continuous bombardment of old satellites colliding with
the Earth. [2]
284
g / N kg–1