Answer:
The gravitational acceleration is 5.03 m/s² on the surface of the planet.
Step-by-step explanation:
Frequency:
The number of complete oscillation per unit second is called frequency.

Angular frequency:
Angular frequency is the product of the oscillation frequency and the angle thought which the object moves.
Angular velocity

Given that,
Number of oscillation= 247, time= 793 s, length of the pendulum=1.31 m

Hz.
Angular velocity


=1.96 rad/s
We know that,

g= gravitational force of the planet
= length of the pendulum
= angular velocity
m/s²
= 5.03 m/s²
The gravitational acceleration on the surface of the planet is 5.03 m/s².