The value of acceleration due to gravity 'g' is inversely proportional to the square of the radius of any heavenly body.
Here, g ∝ 1/(R+h)2 where h is the height of surface from R.
So, if the height increases, the 'g' will decrease. There is more height in the mountain than that in Terai. So, 'g' is higher in Terai than in the mountaions.
From, W = mg
W ∝ g
So, W is higher in Terai than in the mountains.