TS EAMCET 6-Aug-2021 Shift 2 Question Paper

When the lift accelerates with acceleration a, then the normal reaction force N by the elevator on the person is given as∴N−mg=ma (where, m is the actual mass of that person)
⇒‌‌N=m(g+a)=80g
When the lift deaccelerates with acceleration a then, mg−N=ma⇒‌‌N=m(g−a)=64g . . . (ii)
⇒ Dividing Eq. (ii) by Eq. (i), we get
‌

g−a

g+a

=‌

64g

80g

⇒‌‌‌

g−a

g+a

=‌

4

5

⇒‌‌5g−5a=4g+4a
⇒‌‌g=9a
⇒‌‌a=‌

g

9

∴ From Eq. (i), we get, 80g=m(g+a)=m(g+‌

g

9

)
⇒‌‌80g=‌

10g

9

m
⇒‌‌m=‌

80×9

10

=72kg
So, the true weight of that person is 72kg.