Answer:
3.56×10²⁶ Kg.
Explanation:
Note: The gravitational force is acting as the centripetal force.
Fg = Fc........................... Equation 1
Where Fg = gravitational Force, Fc = centripetal force.
Recall,
Fg = GMm/r²......................... Equation 2
Fc = mv²/r............................. Equation 3
Where M = mass of the planet, m = mass of the moon, r = radius of the orbit and G = Universal gravitational constant.
Substituting equation 2 and 3 into equation 1
GMm/r² = mv²/r
Simplifying the equation above,
M = v²r/G .............................. Equation 4.
The period of the moon in the orbit
T = 2πr/v
Making v the subject of the equation,
v = 2πr/T............................. Equation 5
where r = 7.0×10⁷ m, T = 6 h 38 min = (6×3600 + 38×60) s = (21600+2280) s
T = 23880 s, π = 3.14
v = (2×3.14×7.0×10⁷ )/23880
v = 18409 m/s
Also Given: G = 6.67×10⁻¹¹ Nm²/kg²
Also substituting into equation 4
M = 18409²×7.0×10⁷ /(6.67×10⁻¹¹)
M = 3.56×10²⁶ Kg.
Thus the mass of the planet = 3.56×10²⁶ Kg.
