Assuming that the information is not in the Starter set, under the racial descriptions, itself; you can download the Free Basic PDF rules here. Hidden within each of the Racial descriptions you can find the average weight of each race. There is also a table for generating weight on page 33 of the basic rules.
On page 12 of the PDF you will find it says that though shorter, dwarves weigh as much as humans. (125-250 pounds)
On page 14 of the PDF, you will find it says that Elves are more slender than humans weighing only 100 to 145 pounds.
on page 16 of the PDF you will find it says that halfings weigh between 40 and 45 pounds.
and on page 17 of the PDF you will find it says that humans weigh in a range of 125-250 pounds.
On page 33 on the first page of Chapter 4, after saying:
You can decide your character’s height and weight, using the
information provided in your race description or on the Random Height
and Weight table.
it gives the following weight information:
- Human: base weight 110lbs + (2d10 X 2d4lbs).
- Dwarf, hill: base weight 115lbs + (2d4 x 2d6lbs)
- Dwarf, mountain: base weight 130lbs + (2d4 x 2d6 lbs)
- Elf, high: base weight 90lbs + (2d10 x 1d4 lbs)
- Elf, wood: base weight 100 lbs +(2d10 x 1d4 lbs)
- Halfling 35lbs + (2d4 x 1 lbs)
Since all the traps are based off a weight of 100 lbs, this means that basically unless they are a halfling, they will trigger the trap. You can calculate the weight of their equipment as well to see if they trigger it, but it's likely not necessary.
The intention of the rules however is to add the weight of the character plus the weight of the equipment, plus any other weight on the location.