From the given figure, we can note the following:

• Weight of cork in the air (Wa) = 4 N
• Weight of cork in liquid (Wb) = 1 N
• Weight of liquid displaced (Wc) = (Wa - Wb) = 3 N

According to Archimedes' Principle, the upthrust due to water on an object that is partially or wholly immersed in a fluid is equal to the weight of liquid displaced by the object.

Hence, upthrust (U) = Wc = 3 N

The required upthrust when the cork is placed in the liquid is 3 N.