Question

A stationary lift breaks from the top floor of the building and reaches the ground in t = 3 sec. Find the approximate height of the lift from the ground while broken
1. 50 m
2. 47 m
3. 45 m
4. 54 m

Answer 1

Correct Answer - Option 3 : 45 m

CONCEPT:

• The fall of an object under the influence of gravity is known as freefall
• Equations of motion give the idea about characteristics of motion such as velocity, acceleration, and displacement.
• Under the influence of gravity, the above equations of motion become

V = U+gt

\(s =ut+\frac{1}{2}{gt^{2}}\)

V2 = U2 + 2gs

Where U = initial velocity, V = final velocity, ga= acceleration , t = time, and S = height/distance covered

CALCULATION: 

Given - U = 0 m/s, t = 3Sec, a = g = 9.8 m/s²

• The equation of motion is under the influence of gravity

\(\Rightarrow s =ut+\frac{1}{2}{gt^{2}}\) 

Substituting the given value in the above equation

\(\Rightarrow S = 0\times t + \frac{1}{2}gt^{2}\)

\(\Rightarrow S = +\frac{1}{2}\times 10\times 3^{2} = 45 \ meter\)

• Hence option 3 is the answer