Question

How much momentum will a dumb-bell of mass 10 kg transfer to the floor if it falls from a height of 80 cm and does not rebound? Take its downward acceleration to be $10m{s}^{-2}$

• A. $40kgm{s}^{-1}$
• B. $20kgm{s}^{-1}$
• C. $80kgm{s}^{-1}$
• D. $120kgm{s}^{-1}$

Answer 1

The correct option is A $40kgm{s}^{-1}$

Mass of dumb-bell, $m=10kg$; initial velocity, $u=0$; final velocity, $v=?$; distance, $s=80cm=0.8m$; acceleration, $a=10m{s}^{-2}$
We know $v^2-u^2=2as$
$v^2-(0{)}^2=2\times 10\times 0.8$
$v^2=16$
$v=\sqrt{16}=4m{s}^{-1}$
$\therefore$ Momentum of dumb-bell transferred to ground
$=mv=10\times 4=40kgm{s}^{-1}$