F=MA, Force = Mass x Acceleration
Power = Force / Time.
That is a bit cryptic, but required to calculate the motors required. The mass of the sheets is really a small part of the overall calculation. The mass of the mechanics will far exceed the mass of the sheets.
If you were feeding one sheet / hour you could use a clock motor, but one sheet / second is going to require a lot more power. The overall system design also enters into the calculation.
In other words, you have not provided enough information to even make a guess at what is required.