Question

An 80 kg person is parachuting and is experiencing a downward acceleration of $2.8m{s}^{-2}$ . The mass of the parachute is 5 kg. The upward force on the open parachute is (Take $g=9.8m{s}^{-2})$

• A. 595 N
• B. 675 N
• C. 456 N
• D. 925 N

Answer 1

Answer: (A)

Mass of the person $M=80$ kg
Mass of the parachute $m=5$ kg
$\therefore$ Total mass of the system $=M+m=85$ kg
Downward acceleration $a=2.8m{s}^{-2}$
Let upward force $=F$
Applying Newton's II law of motion to this system
$F=\left(m+M\right)g-\left(m+M\right)a$
$orF=\left(m+M\right)\left(g-a\right)$
$F=85\left(9.8-2.8\right)N$
$=85\times 7N$
$F=595N$