81. With g
B
= 9.8128 m/s
2
and g
M
= 9.7999 m/s
2
, we apply Eq. 4-26:
R
M
− R
B
=
v
2
0
sin 2θ
0
g
M
−
v
2
0
sin 2θ
0
g
B
=
v
2
0
sin 2θ
0
g
B
g
B
g
M
− 1
which becomes
R
M
− R
B
= R
B
9.8128
9.7999
− 1
and yields (upon substituting R
B
= 8.09 m) R
M
− R
B
= 0.01 m.