a person stands on a scale inside an elevator at rest. the scale reads 700 n.
a) what is the persons mass?

b) the elevator accelerates upward momentarily at the rate of 1.5 m/s squared. what does the scale read then?

c) the elevator than moves with a steady (uniform) speed of 4 m/s. what does the scale read?

a) The mass of the person, m = 71.43 kg

b) The scale reading when elevator has an acceleration, W = 807.15 N

c) The scale reading when elevator has constant speed, W = 700 N

Explanation:

Given data,

The weight of the person inside the elevator, W = 700 N

The upward acceleration of elevator, a = 1.5 m/s²

The uniform speed of the elevator, v = 4 m/s

a) The mass of the person,

                            m = W /g

                                = 700 N / 9.8 m/s²

                                = 71.43 kg

b) The weight of the person,

                          W = mg + ma

                               = 700 N + 71.43 kg x 1.5 m/s²

                              = 807.15 N

c) When the speed is constant,

                           W = mg

                               = 700 N

The scale reading when the velocity is constant, W = 700 N

your answer is c! hope this : )

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.