Question

You are standing on a bathroom scale in an elevator in a tall building. Your mass is

Answer 1

Answer:

94 kg or 921.6 N

Explanation:

The velocity function is $v(t) = 3t + 0.2t^2$. The acceleration function, a(t), is the time derivative of the velocity function.

$a(t) = \dfrac{d}{dt}v(t) = 3 + 0.4t$

At $t=4$,

$a(4) = 3 + 0.4\times4 = 3+1.6 =4.6\text{ m/s}{}^2$

Because the elevator is going upwards, the net acceleration, $a_N = g + a(4)$ where g us acceleration of gravity.

$a_N = 9.8 + 4.6 = 14.4\text{ m/s}{}^2$

The resultant weight is

$W =m a_N =64\times14.4=921.6 \text{ N}$

Since the bathroom scale is graduated in kg, it's reading is

$m =\dfrac{W}{g}=\dfrac{921.6}{9.8}=94\text{ kg}$