Question

An object is thrown upward to a certain height with a velocity of 3m/s. If the time required to reach the height is 5s. Calculate the height at which it was thrown (hint:( g=10m/s^2)(use second equation of motion).

Answer 1

$\huge\underline{\bold{\red{Answer\::}}}$

$\underline{An \:object \:is\: thrown \:upward \:to\: a \:certain}$ $\underline{height \:with \:velocity\: 3 \:m/s.}$

$\textbf{Here 3 m/s is initial velocity}$

$\underline{If\: the \:time\: required \:to\: reach \:the \:height\: is}$ $\underline{5\: sec.}$

$\textbf{Here 5 sec is time}$

$\underline{Calculate\: the\: height \:at \:which \:it \:was}$ $\underline{thrown.}$

$\textbf{Means we have to find it's height}$

Again.. we have given

$\textbf{u (initial velocity) = 3 m/s}$

$\textbf{t (time) = 5 sec}$

$\textbf{v (final velocity) = 0 m/s}$

$\textbf{a (acceleration) = ?}$

$\textbf{S (height) = ?}$

$\textbf{v = u + at}$

0 = 3 + a (5)

-3 = 5a

5a = -3

a = $\dfrac{-3}{5}$

Now;

s = ut + ½ at²

s = 3 × 5 + $\dfrac{1}{2}$ × $\dfrac{-3}{5}$ × (5)²

s = 15 + $\dfrac{-15}{2}$

s = $\dfrac{30\:-\:15}{2}$

s = $\dfrac{15}{2}$

$\boxed{\boxed{s\: =\: 7.5 \:m}}$