Given data
*The given height of the building h = 56 m
*The distance from the base is d = 45 m
*The value of the acceleration due to gravity is g = 9.8 m/s^2
The formula for the time taken by the lemming is given as
Substitute the known values in the above expression as
The formula for the lemming's initial speed is given as
Substitute the known values in the above expression as
Hence, the lemming's initial speed is v = 13.3 m/s