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(=v_2-v_1)/(t_2-t_1)`

`\begin{gathered} a=(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*9.8+79*2 \\ 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*9.8 \\ 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*9.8-79*2 \\ N=616.2\text{ N} \end{gathered}`