Question

what is the reading on the scale atT equals 1.0 secondswhat is the reading on the scale at T equals 4 point0 secondswhat is the reading on the scale at T equals 8 point0 seconds

Answer 1

Given Data

we have a person whose mass is m= 79 kg. and rides in the elevator.

velocity vs time graph is given.

first look at the free body diagram of a person

now look all the forces which are acting on a person

person in an elevator that is moving upwards

we can write the equation as

$N-mg=ma$

Here N is a normal reaction by the bathroom scale, mg is wight force and a acceleration of the elevator

we can write above equation as

$N=mg+ma\ldots\ldots\ldots(1)$

now we have to calculate acceleration

$a$

we can see the graph

for the increasing the velocity we can write acceleration as

$a\frac{=v_2-v_1}{t_2-t_1}$

$\begin{gathered} a=\frac{4-0}{2-1} \\ a=2m/sec^2 \end{gathered}$

now we can write put the acceleration into equation 1

we have

$\begin{gathered} N=mg+ma \\ N=79\times9.8+79\times2 \\ N=923.2\text{ N} \end{gathered}$

at t =4 seconds no acceleration then a=0

then we can write

$\begin{gathered} N=mg\text{ } \\ N=79\times9.8 \\ N=774.2\text{ N} \end{gathered}$

similarly for t=8 seconds

we have

$a=-2m/sec^2$

from equation (1) we can write as

$\begin{gathered} N=mg-ma \\ N=79\times9.8-79\times2 \\ N=616.2\text{ N} \end{gathered}$