5.5 N
We are given;
We need to calculate the apparent weight when in liquid .
Upthrust = Real weight - Apparent weight
= 10 N - 7 N
= 3 N
we need to know that;
Relative density of a liquid = Upthrust in liquid/Upthrust in water
Therefore;
1.5 = U ÷ 3 N
Upthrust in liquid = 3 N × 1.5
= 4.5 N
But, Upthrust = Real weight - Apparent weight
Therefore;
Apparent weight in Liquid = Real weight - Upthrust
= 10 N - 4.5 N
= 5.5 N
Thus, the weight when the object is immersed in the liquid is 5.5 N