Answer:
The value of g = 0.6168 m/s².
Explanation:
Given that,
On a planet X,
Length of the pendulum(L) = 0.25 meters,
Time period of the pendulum(T) = 4 seconds.
We have to find the 'g' value on the planet.
The 'g' value on a planet can be found by a pendulum with help of the formula,
T = 2π ×
From this, g = 4π² × 
Using the above formula and substituting the values,we get,
g = 0.6168 m/s².
Part a)
Here in this we can use momentum conservation as there is no external force on it

here we know that





now by above equation



Part b)
Final kinetic energy of the system



Initial Kinetic energy of the system will be



So here kinetic energy is decreased for this system
final energy is less than initial energy
So what u do is 2112393921010