Lift Off

Aim:
To measure the vertical lift force produced by a helium filled balloon.
Materials:
meter rule 2 m length of string selection of masses pair of scissors
Method:
The measurement of the lift force can be made in any way, but using only the materials provided.
Conditions:
None.
Time Limit:
30 minutes
Ranking:
The ranking order will be determined by the difference between the estimated force and the force as measured by one of the judges.