I'll be brief.
The height of the 1st floor = 4.3 meters.
For a more accurate value, I calculated the height of 7 floors and got 23 pixels.
https://sun9-12.userapi.com/c858228/v858228876/176bd3/kdLbZD8GxJs.jpg
1)7 * 4,3/23 = 1.309 meters per pixel
2)Diameter of the ball = 550 pixels = 550 * 1.309 = 720 meters (we got 719.95 meters, but I decided to round it up)
Radius of the ball = 360 meters.
3) Volume = 3,14 * 360^3 * 4/3 = 195 333 120 m^3
The ball looks tight enough and I will take 3 ends with a void to get different results:
Low end - 80%
Mid end-70%
High end - 60%
Concrete density = 2200 kg / m^3.
4) Find the mass:
Low end = 195 333 120 * 2200 * 0,2 = 85 946 572 800 kg;
Mid end = 195 333 120 * 2200 * 0,3 = 128 919 859 200 kg;
High end = 195 333 120 * 2200 * 0,4 = 171 893 145 600 kg.
The diameter of the ball = 720 meters = 100 pixels.
The height of the panel is = 768 pixels.
https://sun9-51.userapi.com/c858228/v858228586/173117/ySzNiGX6NyA.jpg
Distance between ball and screen = 720*768/(100*2tan(70/2)) = 5835 meters.
From the moment the Mob started lifting the first buildings to the formation of the ball, it took 35 seconds.
To get acceleration, we will divide the distance by time.
6)a = 5835/35 = 166 m / sec.
Low end: F = 166 * 64 459 929 600 = 1,0700348 × 10^13 kg = Class T
Mid end: F = 166 * 96 689 894 400 = 1,6050522 × 10^13 kg = Class T
High end: F = 166 * 128 919 859 200 = 2,1400697 × 10^13 kg = Class T
Something like that...