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Ksenya-84 [330]
2 years ago
10

Tính hiệu suất nhiệt của động cơ nhiệt biết nhiệt lượng ở nguồn nóng 420,4kJ/kg và nhiệt lượng ở nguồn lạnh 218kJ/kg.

Physics
1 answer:
Travka [436]2 years ago
6 0

Answer:

69

Explanation:

just because

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<em>Magnetite is a Natural magnet</em>

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2 years ago
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Do all of them please and explain
kondaur [170]

At 305 and 309 it was negative because it is going down


at 300 and 301 and 305 it was positive because its going up


at 302/303/304/306/309 she wasn't accelerating at all because it is staying the same

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Does a resistor resist current or voltage
KIM [24]
The answer is current
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3 years ago
When is the velocity of a mass on a spring at its maximum value?
ehidna [41]

Answer:

A.  when the mass has a displacement of zero

Explanation:

The velocity of a mass on a spring can be calculated by using the law of conservation of energy. In fact, the total energy of the mass-spring system is equal to the sum of the elastic potential energy (U) of the spring and the kinetic energy (K) of the mass:

E=U+K=\frac{1}{2}kx^2 + \frac{1}{2}mv^2

where

k is the spring constant

x is the displacement of the mass with respect to the equilibrium position of the spring

m is the mass

v is the velocity of the mass

Since the total energy E must remain constant, we can notice the following:

- When the displacement is zero (x=0), the velocity must be maximum, because U=0 so K is maximum

- When the displacement is maximum, the velocity must be minimum (zero), because U is maximum and K=0

Based on these observations, we can conclude that the velocity of the mass is at its maximum value when the displacement is zero, so the correct option is A.


8 0
3 years ago
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The tension of a guitar string is increased by 40%. By what factor odes the fundamental frequency of vibration change? a. 1.13 b
bogdanovich [222]

Answer:

<h3> b. 1.18</h3>

Explanation:

The fundamental frequency in string is expressed as;

F1 = 1/2L√T/m .... 1

L is the length of the string

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m is the mass per unit length

If the tension is increased by 40%, the new tension will be;

T2 = T + 40%T

T2 = T + 0.4T

T2 = 1.4T

The new fundamental frequency will be;

F2 = 1/2L√1.4T/m ..... 2

Divide 1 by 2;

F2/F = (1/2L√1.4T/m)/1/2L√T/m)+

F2/F = √1.4T/m ÷ √T/m

F2/F = √1.4T/√m ×√m/√T

F2/F = √1.4T/√T

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F2/F = 1.18

F2 = 1.18F

Hence the fundamental frequency of vibration changes by a factor of 1.18

8 0
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