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iragen [17]
3 years ago
14

Một ô tô chuyển động từ A đến B với tốc độ 30m/s rồi lập tức quay lại A với tốc độ 20m/s. Tính tốc độ trung bình trên cả đoạn đi

và về
Physics
1 answer:
viktelen [127]3 years ago
4 0
54 plus 95 is the real answer 3 is everyone’s lucky number one lucky leprechaun is the kind and two daughters are his wives
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A piano of mass 852 kg is lifted to a height of 3.5 m. How much gravitational potential energy is added to the piano? Accelerati
JulsSmile [24]
m=852 \ kg \\ h=3,5 \ m \\ g=9,8 \ m/s^2 \\ \boxed{P_e-?} \\ \bold{Solving:} \\ \boxed{P_e=m \cdot g \cdot h} \\ P_e=852 \ kg \cdot 9,8 \ m/s^2 \cdot 3,5 \ m =8 \ 349,6 \ N \cdot 3,5 \ m \\ \Rightarrow \boxed{P_e=29 \ 223,6 \ J}
7 0
3 years ago
A resistor is connected in series with an AC source that provides a sinusoidal voltage of v of t is equal to V times cosine of b
nekit [7.7K]
<h2>Answer:</h2>

In circuits, the average power is defined as the average of the instantaneous power  over one period. The instantaneous power can be found as:

p(t)=v(t)i(t)

So the average power is:

P=\frac{1}{T}\intop_{0}^{T}p(t)dt

But:

v(t)=v_{m}cos(\omega t) \\ \\ i(t)=i_{m}cos(\omega t)

So:

P=\frac{1}{T}\intop_{0}^{T}v_{m}cos(\omega t)i_{m}cos(\omega t)dt \\ \\ P=\frac{v_{m}i_{m}}{T}\intop_{0}^{T}cos^{2}(\omega t)dt \\ \\ But: cos^{2}(\omega t)=\frac{1+cos(2\omega t)}{2}

P=\frac{v_{m}i_{m}}{T}\intop_{0}^{T}(\frac{1+cos(2\omega t)}{2} )dt \\\\P=\frac{v_{m}i_{m}}{T}\intop_{0}^{T}[\frac{1}{2}+\frac{cos(2\omega t)}{2}]dt \\\\P=\frac{v_{m}i_{m}}{T}[\frac{1}{2}(t)\right|_0^T +\frac{sin(2\omega t)}{4\omega} \right|_0^T] \\ \\ P=\frac{v_{m}i_{m}}{2T}[(t)\right|_0^T +\frac{sin(2\omega t)}{2\omega} \right|_0^T] \\ \\ P=\frac{v_{m}i_{m}}{2}

In terms of RMS values:

V_{RMS}=V=\frac{v_{m}}{\sqrt{2}} \\ \\ I_{RMS}=I=\frac{i_{m}}{\sqrt{2}} \\ \\ Then: \\ \\ P=VI

7 0
3 years ago
Alternating current changes the ____ of the current flow
Anuta_ua [19.1K]

Answer:

Direction

Explanation:

There are two types of electric current:

- DC (Direct current): in a direct current, the direction of the flow of the current is constant; this means that it does not change. This means that the potential difference supplied has always the same direction, so that the electrons travel always in the same direction through the circuit

- AC (Alternating current): in an alternating current, the direction of the flow of the current is constantly reverses. This means that the direction of the potential difference supplied constantly changes, therefore the electrons travel half the time in one direction and half the time in the opposite direction.

5 0
4 years ago
A 45-kg pole vaulter running at 10 m/s vaults over the bar. Her speed when she is above the bar is 1.1 m/s. Neglect air resistan
Lubov Fominskaja [6]

The altitude or height of the pole vaulter as she crosses the bar is 4.04 m.

<h3>What is the height of the pole vaulter?</h3>

The height of the pole vaulter is determined from the change in kinetic energy which is equal to the potential energy at that height.

  • Potential energy = Change in kinetic energy
  • mgh = m(v - u)²/2

h = (v - u)²/2g

h = (10 - 1.1)²/2 * 9.8

h = 4.04 m.

In conclusion, the height is determined from the potential energy at that height.

Learn  more about potential energy at: brainly.com/question/14427111

#SPJ1

7 0
2 years ago
Metals are good conductors of electricity because they _________
Gnesinka [82]

Metals are good conductors because the molecules that are inside the metal are tightly packed together. This is why the heat moves through the metal quickly.

6 0
3 years ago
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