Stacy measures two quantities: the mass of each washer and the force that the washers exert on the force meter. In general, how will the force change as she adds more washers to the meter?

When she adds more washers to the meter, the magnitude of force that is shown on the force meter increases.

Explanation:

The force that the washers exert on the force meter is actually the weight of the washers. Weight is actually a force with gravitation acceleration.

F = W = mg

Where g is gravitational acceleration and its value is 9.81 m/s² and m is the mass of any object. As she adds more washers to the meter so the total mass of the washers increases. As the mass of the washers increases, magnitude of the force (Weight) shown on the force meter increases.