D) If the composition of a sample is fixed, the sample is a pure substance.
Explanation:
A) It can be separated by using physical means, such as filtering.
Of course using physical means as filtration or crystallization we increase the purity of a compound, however sometimes impurities may remain dissolved in the solution or they may co-precipitate with the analysed sample.
B) The components in a pure substance do not have to be in definite ratios.
If the components in a substance do not have definite rations it means the the substance is not pure, it is a mixture of something.
C) If the composition of a sample varies, the sample is a pure substance.
If the composition of a sample varies, it means that different components in the substance are changing so it is a clue that the substance is not pure.
D) If the composition of a sample is fixed, the sample is a pure substance.
If the composition of a sample is fixed, and it can be determined and proven, the substance is pure.
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Answer:
the frequency of the second harmonic of the pipe is 425 Hz
Explanation:
Given;
length of the open pipe, L = 0.8 m
velocity of sound, v = 340 m/s
The wavelength of the second harmonic is calculated as follows;
L = A ---> N + N--->N + N--->A
where;
L is the length of the pipe in the second harmonic
A represents antinode of the wave
N represents the node of the wave
The frequency is calculated as follows;
Therefore, the frequency of the second harmonic of the pipe is 425 Hz.
Answer:
1) D, 2) D, 3) B, 4) B, 5) C
Explanation:
You are asked to select the correct answer
1) The conservation of energy is one of the most important principles of physics that allows solving countless problems in life.
the correct answer is D
2) when a body falls, the gravitational potential energy is transformed into kinetic energy and both are transformed into thermal energy
the correct answer is D
3) When the gravitational potential energy is maximum, the kinetic energy is minimum and when the kinetic energy is maximum, the gravitational energy is minimum.
Correct answer B
4) speed is defined by
v = x / t
so the correct answer is B in the SI system
5) when we repeat a measurement several times, the random or statistical errors decrease, therefore the confidence of the measurement increases.
The correct answer is C
