Given; m = 2kg; h = 10m;
s = 2cm = 2 × 10-2 m;F = ?
The final velocity of the object on reaching the sand’s surface:
\(v_{1}=\sqrt{2 g h}=\sqrt{2 \times 9.8 \times 10}=14 \mathrm{ms}^{-1}\)
Initial kinetic energy of the object
K1 = \(\frac{1}{2} m v_{1}^{2}\) mvf = \(\frac{1}{2}\) × 2 × 14 × 14
or K1 = 196 J
The final kinetic energy of the object
K2 = 0
If resistive force be F, then
W = FS
Now using work-energy theorem