Question

Suppose you wanted to throw a steel bar vertically to a height of 20m. the bar weighs 30kg. how does the length of the bar affect the answer

Answer 1

suppose the length of bar is x m.
now you throw it vertically up. As the top of the bar will touch 20 m you will get success.
that means that distance of top point will only matter.
Now distance that the top point needs to travel is only 20-x. I think this might be helpful.

Answer 2

W = F x d
Force(F) will be same regardless of the lenght since the mass will be constnt at 30kg and acceleration will be -9.8m/s^2. Distance(d) is how much the bar will travel, so when the forces are equal the length of the bar will decide the amount of work done since the longer the bar, the less work done. And if you consider force applied per time, you will have to apply the force for less amount of time