A

To calculate the work done by the paddle wheel, we first determine the gravitational potential energy lost by the 50-kg weight as it falls through a distance of 2 m. The formula for gravitational potential energy (PE) is given by:
PE = mgh
where:
- m = mass (50 kg)
- g = acceleration due to gravity (approximately 9.81 m/s²)
- h = height (2 m)

Now substituting the values:
PE = 50 \, \text{kg} \times 9.81 \, \text{m/s}^{2} \times 2 \, \text{m}
PE = 50 \times 9.81 \times 2 = 981 \text{ J}

The work done by the paddle wheel is equal to the energy transferred to heat, which is 981 J.
Thus, the heat that must be transferred to result in an equivalent effect is 981 J.