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2.Motion in Straight Line
hard
Four marbles are dropped from the top of a tower one after the other with an interval of one second. The first one reaches the ground after $4$ seconds. When the first one reaches the ground the distances between the first and second, the second and third and the third and forth will be respectively
A
$35, 25$ and $15 \,m$
B
$30, 20$ and $10 \,m$
C
$20, 10$ and $5\, m$
D
$40, 30$ and $20 \,m$
Solution
(a) For first marble, ${h_1} = \frac{1}{2}g \times 16 = 8g$
For Second marble, ${h_2} = \frac{1}{2}g \times 9 = 4.5g$
For third marble, ${h_3} = \frac{1}{2}g \times 4 = 2g$
For fourth marble, ${h_4} = \frac{1}{2}g \times 1 = 0.5g$
$\therefore {h_1} – {h_2} = 8g – 4.5g = 3.5g$ $= 35m.$
${h_2} – {h_3} = 4.5g – 2g = 2.5g = 25m$ and
${h_3} – {h_4} = 2g – 0.5g = 1.5g = 15m$.
Standard 11
Physics
