A real current source has
a. Zero internal resistance
b. Infinite internal resistance
c. A small internal resistance
d. A large internal resistance

A motor applies a $5000-\mathrm{N}$ force and raises an elevator 10 stories. If each story is $4 \mathrm{~m}$ tall, how much work does the motor do?

A motor coil having an inductance of $8 \text{ H}$ is in parallel with a $2 \ \mu\text{F}$ capacitor and a resistor of unknown value. The response of the parallel combination is determined to be critically damped. (a) Determine the value of the resistor. (b) Compute $\alpha$. (c) Write the equation for the current flowing into the resistor if the top node is labeled $v$, the bottom node is grounded, and $v=Ri_r$. (d) Verify that your equation is a solution to the circuit differential equation,

$$\frac{d^2i_r}{dt} + 2\alpha\frac{di_r}{dt}+\alpha^2i_r = 0$$

A box that weighs 575 N is lifted a distance of 20.0 m straight up by a cable attached to a motor. The job is done in 10.0 s. What power is developed by the motor in W and kW?

A rocket is fired vertically and ascends with constant acceleration $a=100 \mathrm{m} / \mathrm{s}^{2}$ for 1.0 min. At that point. the rocket motor shuts off and the rocket continues upward under the influence of gravity. Find the maximum altitude acquired by the rocket and the total time elapsed from the take-off until the rocket returns to the earth. Ignore air resistance.

How is a galvanometer similar to a motor? How is it different?

A real voltage source has
a. Zero internal resistance
b. Infinite internal resistance
c. A small internal resistance
d. A large internal resistance

What structures make up a motor unit?

What is meant by the term motor unit recruitment?

A $9.00-\mathrm{V}$ battery is connected through a switch to two identical resistors and an ideal inductor, as shown in the figure. Each of the resistors has a resistance of $100 . \Omega$, and the inductor has an inductance of $3.00 \mathrm{H}$. The switch is initially open. d) After a long time ( $>10.0 \mathrm{~s}$ ), the switch is opened again. Immediately after the switch is opened, what is the current in resistor $R_1$ and in resistor $R_2$ ?

A 15-kg motor is supported by four springs, each of constant $40 \mathrm{kN} / \mathrm{m}$. The unbalance of the motor is equivalent to a mass of $20 \mathrm{~g}$ located $125 \mathrm{~mm}$ from the axis of rotation. Knowing that the motor is constrained to move vertically and that the damping factor $c / c_c$ is equal to $0.4$, determine the range of frequencies for which the amplitude of the steady-state vibration of the motor is less than $0.2 \mathrm{~mm}$.

Distinguish between upper and lower motor neurons.

The current through a 100-mH inductance is given by i(t) = exp(-t) sin(10t) in which the angle is in radians. Determine the voltage across the inductance. Then, use the computer program of your choice to plot both the current and the voltage for $0 \leq t \leq 3 s.$

Give the meanings of the following terms.

motor aphasia _________________________________________________