Question

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

• 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 $a=2.8 \, m s^{- 2}$
Let upward force $=F$
Applying Newton's II law of motion to this system
$F=\left(m + M\right)g-\left(m + M\right)a$
$or \, \, F=\left(m + M\right)\left(g - a\right)$
$F=85\left(9.8 - 2.8\right)N$
$=85\times 7 \, N$
$F=595 \, N$