Q. A particle of mass 100 g is thrown vertically upwards with a speed of $5ms^{- 1}$.The work done by the force of gravity during the time, the particle goes up is
A) $- 0.5\ J$
B) $- 1.25\ J$
C) $\ \ \ 1.25\ J$
D) 0.5 J
Explanation
(b) The height $(h)$ traversed by particle while going up is
$\ h = \frac{u^{2}}{2g} = \frac{25}{2 \times 9.8}$
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work done by gravity force=$mg.h$
$= 0.1 \times g \times \frac{25}{2 \times 9.8}\cos{180{^\circ}}$
[angle between force and displacement is $180{^\circ}$]
$\therefore\ \ \ \ \ \ \ \ W = - 0.1 \times \frac{25}{2} = - 1.25\ J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.