Question

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

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

Answer 1

The correct option is A

$595N$

Step 1: Given Data and assumptions:

Mass of person, $M=80kg$

Mass of parachute, $m=5kg$

Downward acceleration, $a=2.8m{s}^{-2}$

Acceleration due to gravity, $g=9.8m{s}^{-2}$

Let, the upward force act on the parachute is $F$

$F_g$ is taken as positive because it is the force acting due to gravitation. So it is acting in the downward direction.

$F_a$ is taken as negative because it is the force acting in the upward direction.

Step 2: Formula used:

Newton's 2nd law,

$F=ma$

Where, $F=$the net force acting on the body

$m=$mass of the body

$a=$acceleration of the body

Step 3: Calculating the force:

$\left(M+m\right)g-F=\left(M+m\right)a$

$\Rightarrow$$\left(80+5\right)\times 9.8-F=\left(80+5\right)\times 2.8$

$\Rightarrow$ $F=85\times 9.8-85\times 2.8$

$=85\times \left(9.8-2.8\right)$

$=85\times 7$

$=595N$

Hence, option $\left(A\right)$ is the correct answer.