"Eles vão pesar o cachorro."

Translation: They are going to weigh the dog.

[bmathe9]

The deffinition for "pesar" is given as "sorrow." Is it an expression for it to mean weigh?

[Paulenrique]

As a verb its "to weigh", as a noun its is sorrow. Weight is "peso"

[Woody]

Why is the present tense "They go to weigh the dog" wrong?

[Paulenrique]

It is a future clause. (Another possibility: "....are going to....")