TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Momentum is directly related to both mass and velocity.

SOLUTION: Momentum is directly related to both mass and?

PROBLEM: Stringed instruments can help show the relationship between tension and frequencies in strings.

SOLUTION: Stringed instruments can help show the relationship between tension and what in strings?

PROBLEM: The quarks in a particle are confined, meaning individual quarks cannot be directly observed.

SOLUTION:
The quarks in a particle are confined, meaning individual quarks cannot be what?