Can the Telekinesis spell be used to move attached objects, like a city gate?

Question

The object-targeting option of the Telekinesis spell (PHB, p. 280-281) says:

You can try to move an object that weighs up to 1,000 pounds. If the object isn't being worn or carried, you automatically move it up to 30 feet in any direction, but not beyond the range of this spell.

[...]

You can exert fine control on objects with your telekinetic grip, such as manipulating a simple tool, opening a door or a container, stowing or retrieving an item from an open container, or pouring the contents from a vial.

The idea of ripping a gate off its hinges with my mind gets me power drunk giddy.

The spell rules don't specifically address a situation of trying to move an object that's connected to other objects by something like brick mortar or hinges.

Is this something that's up to DM discretion?

Answer 1

Telekinesis may reasonably be able to rip attached objects from their moorings.

tl;dr Use a spell check with DC equivalent to what the Strength check would be.

Telekinesis can extract an object from the grip of a creature with an opposed Strength check. A creature ripping an object from its attachment would require a Strength check with DC set by the GM. It is a short leap to use telekinesis to rip an object from its attachments similarly to how a creature pulling on it would.

The change would be that instead of a Strength check, the caster is making a spellcasting ability check as that follows the example for taking a held object by force.

If the object is worn or carried by a creature, you must make an ability check with your spellcasting ability contested by that creature's Strength check.

For example, if the DC of a Strength check to rip a door from its hinges is 25, then that's the DC of the spellcasting ability check to do so with telekinesis.

Answer 2

Yes: an attached object is still an object

The definition of objects is given in the rules on p. 246 as:

For the purpose of these rules, an object is a discrete, inanimate item like a window, door, sword, book, table, chair, or stone, not a building or a vehicle that is composed of many other objects.

Both a window or door are normally attached to a building with hinges, and a gate is essentially just an oversized double-door. This is exactly covering your use case. You will be able to affect a gate with telekinesis.

Wether you will be able to rip it out of its hinges depends on how strong those hinges are, and would require a check as DC discussed in the accepted answer. The DM will have to rule if the gates are too strong to even allow a check, or at what level to set the check's DC.

Benchmarks: A character with Strength 20 can be expected exert enough force to move 600 pounds (see PHB p. 176, Push, Drag, or Lift), and city gates that are there to protect the city from invaders should be expected to be built strong enough to withstand the capacity of a single human, even a very strong one. A hill giant, which we might assume should be able to rip out city gates, could exert enough to move 2,520 pounds. Telekinesis can move a maxium of 1,000 pounds, somewhat more than the human but far less than the giant.

DCs: Telekinesis is a 5th level spell, so assuming that the caster has maxed their spellcasting ability score, they would have at least +9 on these rolls. If the DC were 25, this would give them a 25% chance to succeed, and they could rattle the gates a few turns before they came off. If the DC was 30, it would only be possible for level 13 or higher casters (with +10 on their roll) to eventually rip them out.