Correct Answer - 40 kg

Mass of the dumbbell, m = 10 kg

Distance covered by the dumbbell, s = 80 cm = 0.8 m

Acceleration in the downward direction, `a = 10 m//s^(2) `

Initial velocity of the dumbbell, u = 0

Final velocity of the dumbbell (when it was about to hit the floor) = v

According to the third equation of motion:

` v^(2)= u^(2) + 2as`

` v^(2)= 0 + 2 (10) 0.8 `

v= 4 m/s

Hence, the momentum with which the dumbbell hits the floor is

= mv ` = 10 xx 4 kg ms^(-1)`

` = 40 kg ms^(-1)`