Physics, 23.07.2019 08:00, Lscifa

Ineed with 6. i don’t know how to approach this problem.

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-- The total resistance of the circuit is (2 ohms in the resistor) plus
(1 ohm in the light bulb) = 3 ohms.

-- The current in the circuit is (3v)/(3 ohms) = 1 Amp

-- The voltage across the 2-ohm resistor is (1 Amp) x (2 ohms) = 2 volts
(points 1 and 2)

-- The voltage across the 1-ohm light bulb is (1 Amp) x (1 ohm) = 1 volt
(points 2 and 3)

-- The voltage between points 3 and 4 is (1 Amp) x (zero ohms) = zero

-- If the bulb was replaced with wire, the total resistance in the circuit
would be only the 2-ohm resistor.

-- The current would be (3v)/(2 ohms) = 1.5 Amp.

-- The resistor would be connected directly across the battery.
So the entire 3 volts would appear across the resistor.
Points 2 to 3 and points 3 to 4 would be only wire, with no voltage drop.

answered: Guest

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

$x(t)=ax(x-6)$

where $a$ is unknown. because the position is parabolic, there is symmetry about the midpoint at $t=3$ , and we know that

$x(3)=10\implies -9a=10\implies a=-\dfrac{10}9$

so that the position function is

$x(t)=-\dfrac{10}9x(x-6)$

which means the velocity is

$v(t)=\dfrac{\mathrm dx}{\mathrm dt}=-\dfrac{20}9x+\dfrac{60}9$

then the total distance traveled is

$\displaystyle\int_{t=0}^{t=6}|v(t)|\,\mathrm dt=\left\{\int_{t-0}^{t=3}-\int_{t=3}^{t=6}\right\}v(t)\,\mathrm dt=20$

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at $x=0$ and ends at $x=0$ , so its displacement is 0.

answered: Guest

Answer sample (c); // would be best because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the smallest;