Question

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.$(g=10m/s^2)$

• A. $200$J
• B. $400$J
• C. $600$J
• D. $900$J

Answer 1

The correct option is B $400$J

It is known that

$\Delta U=mgh$, so

$\Delta U=0.2\times 10\times 200=400J$

From energy conservation we know that:

$\therefore$ Gain in $K.E.$= decrease in $P.E.=400J$.

so Option B is correct.