Q.
If a body of mass $200\ g$ falls from a height $200\ m$ and its total P.E. is converted into K.E. at the point of contact of the body with earth surface, then what is the decrease in P.E. of the body at the contact ( $g = 10\ m/s^{2}$)
A) $200\ J$
B) $400\ J$
C) $600\ J$
D) $900\ J$
Explanation
(b) $\mathrm{\Delta}U = mgh = 0.2 \times 10 \times 200 = 400J$
$\therefore$ Gain in K.E. = decrease in P.E. $= 400\ J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.