Question

A body falling under gravity covers two points A and B separated by 80 m in 2s. The distance of upper point A from the starting point is ________ m (use g = 10 ms^–2)

Answer 1

Correct Answer: 45

Given:
- Distance between A and B = \(80 \, \text{m}\),
- \(t = 2 \, \text{s}\),
- \(g = 10 \, \text{m/s}^2\).

Using the equation of motion:

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

For motion from A to B:

\(-80 = v_1 t - \frac{1}{2} g t^2\)

Substituting values:

\(-80 = v_1 \cdot 2 - \frac{1}{2} \cdot 10 \cdot 2^2\)

\(-80 = 2v_1 - 20\)

\(-60 = 2v_1 \implies v_1 = -30 \, \text{m/s}.\)

For motion from 0 to A:

Using the equation:

\(v_1^2 = u^2 + 2gS\)

\(30^2 = 0 + 2 \cdot 10 \cdot S\)

\(900 = 20S \implies S = 45 \, \text{m}.\)

The Correct answer is: 45 m