A motor running from a 220-V line is lifting a mass of 35 kg against Earth's gravity at a constant speed of 6.0 m/s.If we assume 100% efficiency,the current required is
A)0.27 A
B)9.4 A
C)7.7 A
D)3.3 A
E)4.7 A

Question

Quizplus · Accepted Answer

The power required to lift the mass can be calculated using the formula $P = F \cdot v$, where $F$ is the force and $v$ is the velocity. The force $F$ needed to lift the mass is equal to the weight of the mass, which is $mg$, where $m$ is the mass and $g$ is the acceleration due to gravity (approximately $9.8 \, \text{m/s}^2$). Thus, $F = 35 \, \text{kg} \cdot 9.8 \, \text{m/s}^2 = 343 \, \text{N}$. The power $P$ is then $343 \, \text{N} \cdot 6.0 \, \text{m/s} = 2058 \, \text{W}$.The current $I$ required can be found using the formula $P = VI$, where $V$ is the voltage and $P$ is the power. Rearranging for $I$, we get $I = \frac{P}{V} = \frac{2058}{220} \approx 9.4 \, \text{A}$.

A Motor Running from a 220-V Line Is Lifting a Mass