Sand is being dropped on a conveyer belt at the rate of $2 \mathrm{~kg}$ per second. The force necessary to…
Sand is being dropped on a conveyer belt at the rate of $2 \mathrm{~kg}$ per second. The force necessary to keep the belt moving with a constant speed of $3 \mathrm{~ms}^{-1}$ will be
$12 \mathrm{~N}$
$6 \mathrm{~N}$
zero
$18 \mathrm{~N}$
Solution
Here, rate of fall of sand on conveyer belt,
$
\frac{d m}{d t}=2 \mathrm{~kg} \mathrm{~s}^{-1}
$
Conveyer belt speed $v=3 \mathrm{~ms}^{-1}$ Force $F=$ ?
$
F=v \frac{d m}{d t}=3 \times 2=6 \mathrm{~N}
$