Q87 / 125 · BITSAT 2013 · Physics
A man runs at a speed of $4 \mathrm{~m} / \mathrm{s}$ to overtake a standing bus. When he is $6 \mathrm{~m}$ behind the door at $\mathrm{t}=0,$ the bus moves forward and continuous with a constant acceleration of $1.2 \mathrm{~m} / \mathrm{s}^{2}$. The man reaches the door in time $\mathrm{t}$. Then,
- Correct answerA$4 \mathrm{t}=6+0.6 \mathrm{t}^{2}$
- B$1.2 \mathrm{t}^{2}=4 \mathrm{t}$
- C$4 t^{2}=1.2 t$
- D$6+4 \mathrm{t}=0.2 \mathrm{t}^{2}$
Solution
Let us draw the figure for given situation,

$\Rightarrow \quad 4 \mathrm{t}=6+\frac{1}{2} \times 1.2 \times \mathrm{t}^{2}$ $\Rightarrow \quad 4 \mathrm{t}=6+0.6 \mathrm{t}^{2}$

$\Rightarrow \quad 4 \mathrm{t}=6+\frac{1}{2} \times 1.2 \times \mathrm{t}^{2}$ $\Rightarrow \quad 4 \mathrm{t}=6+0.6 \mathrm{t}^{2}$
Hence, the correct answer is option: 'A'.