JEE Main 2021 — Laws Of Motion Question with Solution

The apparent weight $W_{\text{app}}$ of a person in an elevator moving with acceleration is given by:

$$W_{\text{app}}=m(g-a)$$

where:

• $W_{\text{app}}$ is the apparent weight,
• $m$ is the mass of the person,
• $g$ is the acceleration due to gravity,
• $a$ is the acceleration of the elevator.

Given that the person's mass is 60 kg, the acceleration due to gravity is 10 m/s², and the acceleration of the lift is 1.8 m/s², we can substitute these values into the formula:

$$W_{\text{app}}=60\text{kg}\times (10{\text{m/s}}^2-1.8{\text{m/s}}^2)=60\text{kg}\times 8.2{\text{m/s}}^2=492\text{N}$$

So, the apparent weight of the person when the lift descends with a uniform downward acceleration of 1.8 m/s² will be 492 N.