Prove that if a body is thrown vertically upward, time of ascent is equal to time of descent.

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7. MOTION

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Prove that if a body is thrown vertically upward, the time of ascent is equal to the time of descent.

Option A

Option B

Option C

Option D

Solution

For upward motion

$v=u-g t$ or $0=u-g t_{1}$

or $t_{1}=\frac{u}{g}$ $….(1)$

For downward motion

$v=u+g t_{2}$ or $v=0+g t_{2}$

As the body falls back to the earth with the same velocity, it was thrown vertically upwards.

$\therefore \quad v=u$

$u=0+g t_{2}$ or $t_{2}=\frac{u}{g}$ $…(2)$

From $(1)+(2)$ the statement is proved.

Standard 9

Science

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