Engineers modify an industrial floor-cleaning robot by fitting a new scrubbing unit. Before the modification, the robot travels 0.40 m after its brakes engage before coming to rest. After the modification, this distance is 0.60 m. The robot begins braking at the same speed in both tests, and its braking system exerts the same constant force.
What is the percentage increase in the mass of the robot?
67%67\%67%
150%150\%150%
50%50\%50%
33%33\%33%