[填空题]
A box half filled with sand is pulled by a motor at a constant speed of2${2ms^{-1}}$ on a frictionless surface. During the motion, sand is added to the box from above at a constant rate of ${{\sigma}kgs^{-1}}$
State the condition related to the mass of an object in order for the equation ${F_{net}}$=ma to be equivalent to the equation ${F_{net}}$=${\frac{{\Delta}p}{t}}$.
1
The force applied by the motor on the box is 0.11N. Determine ${\sigma}$ ${kgs^{-1}}$
2
The motor has an efficiency of 75%. Calculate the total power provided to the motor. W
2
