Let the radius of earth from surface of earth is R and the height equal to half the radius of earth from surface of earth is h.
The acceleration on the surface of earth due to gravity is given as,
g=GMR2
The acceleration at a height due to gravity is given as,
g′=GMh2
=GM(R2)2
=4g
=4×10
=40m/s2
Thus, the value of acceleration at a height due to gravity is 40m/s2.