Question

Plzzzz help me.......
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Answer 1

${\mathfrak{\underline{\purple{\:\:\: Given:-\:\:\:}}}}$

$\:\:\:\:\bullet\:\:\:\sf{Mass \ of \ boulder = 30 \:kg}$

$\:\:\:\:\bullet\:\:\:\sf{Initial\: velocity= 10\:m/s}$

$\:\:\:\:\bullet\:\:\:\sf{Final\: velocity= 0\:m/s}$

$\:\:\:\:\bullet\:\:\:\sf{Retarding \ force = -10N}$

${\mathfrak{\underline{\purple{\:\:\:To \:Find:-\:\:\:}}}}$

$\:\:\:\:\bullet\:\:\:\textsf{After how long will the boulder stop ?}$

${\mathfrak{\underline{\purple{\:\:\: Solution:-\:\:\:}}}}$

☯ By using F = ma

$\dashrightarrow\:\: \sf{ Force = mass \times acceleration}$

$\dashrightarrow\:\: \sf{-10=30\times a}$

$\dashrightarrow\:\: \sf{-10=30a}$

$\dashrightarrow\:\: \sf{a = -\dfrac{1}{3}m/s^{2}}$

☯ Now, using 1st equation of motion:-

$\dashrightarrow\:\: \sf{v = u +at}$

$\dashrightarrow\:\: \sf{0= 10-\dfrac{t}{3}}$

$\dashrightarrow\:\: {\boxed{\bf{t = 30\:s}}}$