I have learned in thermodynamics that it is impossible for a cyclic
system that is receiving energy as heat from one and only one thermal
reservoir to produce a net positive amount of work to the
That is correct. The applicable statement of the second law is the following Kelvin-Planck statement:
No heat engine can operate in a cycle while transferring heat with a single heat reservoir
I understand the other version of this statement that it is impossible
for a cyclic system to convert all the energy input to work (100%
efficiency) easily, but I don't understand how a cyclic system can
produce a net negative amount of work (from surrounding to the system)
Not sure what you mean by the "other version", but net negative work (i.e., net work input instead of net work output) is done when you reverse the heat engine cycle making it a refrigeration or heat pump cycle. For the refrigeration and heat pump cycle the following Clausius's statement of the second law applies:
No refrigeration or heat pump cycle can operate without a net work
The refrigeration or heat pump cycle moves heat from a low temperature reservoir and transfers it to a high temperature reservoir. Since, as I'm sure you are aware, heat does not flow naturally from cold to hot, in order to do this work must be done on the working fluid. Work done on a system is negative.
For a refrigeration or heat pump cycle we don't talk about efficiency. We talk about the Coefficient of Performance, or COP. This equals the desired heat transfer divided by the work input required, or
For a refrigerator:
For a heat pump:
$Q_L$ = the heat transfer from the low temperature environment
$Q_H$ = the heat transfer to the high temperature environment
$W$ = the work input (negative work) required to cause the transfer.
Please explain with a simple practical example how a cycling system
which only communicates with one thermal reservoir can be subject to
work done on it, and not able to to do work on the surrounding.
An example is an ideal gas that undergoes a free adiabatic expansion followed by a reversible isothermal compression.
We have an insulated rigid chamber that is divided into two parts, one containing an ideal gas and the other a vacuum. An opening is created in the barrier between the two parts allowing the gas in one part to spontaneously and rapidly expand into the evacuated part. This is an irreversible process (You would not expect the gas to spontaneously return to its original part leaving a vacuum behind).
Since the chamber walls are rigid, there is no boundary work done ($W=0$) and since it is insulated there is no heat transfer ($Q=0$). From the first law, closed system, $\Delta U=Q-W=0$. If the gas is an ideal gas, then there would also be no temperature change since internal energy of an ideal gas is a function of temperature only.
Now in order to return the gas to its original state we remove the insulation and insert a frictionless piston into the chamber. We then perform a reversible isothermal (constant temperature) compression returning the gas to its original volume and pressure. Since the process is isothermal $\Delta T=0$, $\Delta U=0$ and $Q=W$ where $Q$ is the heat rejected to the surroundings and $W$ is the compression work done on the gas.
The end result is we have a cycle in which work is done exchanging heat with a single reservoir. But the key is that the work done is negative work. The surroundings does work on the gas and not the other way around. This does not violate the Kelvin-Planck statement of the second law because it applies to a heat engine and a heat engine is one that takes in heat from the surroundings and produces net work on the surroundings (positive work).
Hope this helps.