Because we wish to have a sustainable future. The current dependence on fossil fuel means that there will be a point when humans have no fuel to use because fossil fuels are a non-renewable resource.
Answer:
i.e.

Explanation:
Given:
angular speed,
mass of the disk, 
radius of the disk, 
mass of the chunk, 
radius of the chunk, 
We know that the angular momentum is given by:

and moment of inertia for a disc:

According to the conservation of angular momentum, the final angular momentum is equal to the initial angular momentum.




We know, U = mgh
Substitute the known values,
19.6 = m * 9.8 * 8
m = 19.6 / 78.4
m = 1/4
In short, Your Answer would be 1/4 Kg
Hope this helps!
A trippy asssssss body..........