Question

A person is standing on a weighing-scale and observes that the reading is $60\,kg$ . He then suddenly jumps up and observes that reading goes to $70\,kg$ . Then his maximum upward acceleration is

• A. $0$
• B. $1.4\,m/s^{2}$
• C. $1.63\,m/s^{2}$
• D. $9.8\,m/s^{2}$

Answer 1

Answer: (C)

$1.63\,m/s^{2}$

Answer 2

Initial reading of the machine is $60\, kg$.
Therefore, mass of the person, $m=60\, kg$ Final reading is $70\, kg$.
Thus, extra force applied on the person is
$\Delta F=(70-60) \times 98=98\, N$
Hence upward acceleration of the person is
$a=\frac{\Delta F}{m}=\frac{98}{60}=1.63\, m / s ^{2}$