A person standing on a spring balance inside a stationary lift measures 60 kg. The weight of that person if the lift descends with uniform downward acceleration of 1.8 m s$$^{-2}$$ will be ______ N. [$$g = 10$$ m s$$^{-2}$$]

The person has a mass of $$m = 60$$ kg. When the lift descends with a uniform downward acceleration $$a = 1.8$$ m s$$^{-2}$$, the apparent weight measured by the spring balance is reduced because both the person and the lift are accelerating downward.

Applying Newton's second law in the vertical direction, the net force on the person is $$mg - N = ma$$, where $$N$$ is the normal reaction (apparent weight). Solving for $$N$$:

$$N = m(g - a) = 60(10 - 1.8) = 60 \times 8.2 = 492$$ N

Therefore, the weight of the person as measured in the descending lift is $$\mathbf{492}$$ N.