Answer: acceleration due gravity = 619.5 m/s²
Explanation: The relationship between the period of a pendulum, length and acceleration due to gravity is given as
T =2π * (√l/g)
T = period = 0.25s
l = length of pendulum = 1.02m
g = acceleration due to gravity on the unknown planet
0.25 = 2π * (√1.02/g)
By squaring both sides, we have that
0.25² = 4π² * (1.02/g)
0.25² * g = 4π² * 1.02
g = 4π² * 1.02/ 0.25²
g = 40.26756/ 0.0625
g = 619.5m/s²