Browse Questions

# A body of 0.02 kg falling from height 5 m into a pile of sand.The body penetrates the sand a distance of 5cm before stopping what force has the sand exerted on the body?

$(a)\;1.96\;N \quad (b)\;-19.6 \;N \quad (c)\;-0.196 \;N \quad (d)\;0.0196\;N$

v-velocity with which the body reaches the sand
$v^2=u^2+2as$
$\quad=2 \times 9.8 \times 5$
$\quad=98$
It penetrates send 0.05 m and comes to stop
$a=\large\frac{-98}{2 \times 0.05}$
$\quad= -980 m/s^2$
retarding force$= m \times a$
$\qquad=0.02 \times -980$
$\qquad=-19.6 N$
Hence b is the correct answer.

edited Feb 10, 2014 by meena.p