When weighing an object with a pallet balance, the weighed object is placed on the right board and the weight is placed on the left board. If the balance is balanced, there are 100g and 2 on the left

When weighing an object with a pallet balance, the weighed object is placed on the right board and the weight is placed on the left board. If the balance is balanced, there are 100g and 2 on the left panel. D

Test analysis: According to the structure of the balance, the reading should be the mass of the object on the left disk = the mass of the weight on the right disk+the calibration value of the marching code. In this problem, the result can be obtained by exchanging objects and weights. According to the structure of the balance, 100g+20g= object mass +4g, so the object mass is: 120g-4g = 65438+. So choose D.

Comments: When using the sky, the weighed object should be placed on the left tray and the weight should be placed on the right tray. Conversely, the weight can be regarded as an object with a fixed mass, while the object can be regarded as an object with an unknown mass.