1. What do we know? Fg = 78.6 N Fg = mg = (8)(9.8) = 78.4 N 1.
m1 = mass of the object = 8 kg m2 = mass of the earth = × 1024 kg d = distance between the center of the earth and
the center of the object = 6370 km
G = 6.67 x Nm2/kg2
Fg = 78.6 N
REMEMBER
g = 9.8 m/s2 is only valid for an object ON THE EARTH”S SURFACE
This could have been solved in a much easier manner
Fg = mg = (8)(9.8) = 78.4 N

2. What do we know? Fg = 3.74 x 1022 N 1 AU = 1.5 x 108 km2.
What do we know?
Fg = 3.74 x 1022 N
m1 = mass of Saturn = 5.69 x 1026 kg m2 = mass of the sun = 2.0 × 1030 kg d = distance between the center of Saturn and
the center of the sun = 9.5 AU
Fg = ?;T = ? s
1 AU = 1.5 x 108 km
d = x 1012 m
This could have been solved in a much easier manner
REMEMBER
This equation is only valid for two objects ORBITING THE SAME CENTRAL BODY
T =9.25 x 108 s
29.3 years
29.3 years

3. What do we know? m2 = 7.2 x 1022 kg T = 2.4 x 106 s = 28 days 3.
Fg = force of attraction between earth and moon = 1.9 x 1020 N m1 = mass of the earth = 5.98 × 1024 kg d = distance between the center of earth and
the center of the moon = 3.9 x 105 km
G = 6.67 x Nm2/kg2
m2 = 7.2 x 1022 kg
T = 2.4 x 106 s = 28 days

4. Fg = 3.64 x 10-47 N m = 9.0 x 10-31 kg m1 = m2 (m)(m) = m2 4.
m1 = 1.67 x kg m2 = 9.11 × kg d = x m
G = 6.67 x Nm2/kg2 5.
Fg = 5.42 x N
d = 1.00 m m1 = m2 = ?
Fg = 3.64 x N
m1 = m2 (m)(m) = m2
m = 9.0 x kg

5. m = 7.3 kg Fg = 72 N EARTH SATURN Fg = 76 N Fg = 4.0 x 10-8 N 6.
d = 0.30 m m1 = m2 = ?
radius of Saturn =60,280 km 6.
m = 7.3 kg
Fg = 72 N
EARTH
SATURN
Fg = 76 N

6. 7.
T = 23 hrs
m1 = 5.69 × 1026 kg G = 6.67 x Nm2/kg2
This is the radius of the moon’s orbit; we must subtract the planet’s radius to determine altitude above the planet
R = 1.88 x 108 m
- 60,268,000 m
1.27 x 108 m = 127,000 km