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3 years ago

Which of these statements is not true?

Physics

2 answers:

Mrrafil [7]3 years ago

6 0

Atoms of isotopes of an element have different numbers of protons.

protons in the same element never change only neutons vary

lorasvet [3.4K]3 years ago

3 0

From the given chemistry question above, the correct answer would be option C. The statement that is not considered true is that, atoms of isotopes of an element have different numbers or protons. The rest of the statements above are all correct.

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When radioactive tracers are used for medical scans, the tracers both decay in the body via radiation, as well as being excreted

irinina [24]

Answer:

Effective half-time of the tracer is 3.6 days

Explanation:

The formula for calculating the decay due to excretion for the first process is ;

$\frac{dN_1}{dt } = - \lambda _e N_o$

here ;

$N_o$ = initial number of tracers

Then to the second process ; we have :

$\frac{dN_2}{dt } = - \lambda _e N_o$

The total decay is as a result of the overall process occurring ; we have :

$\frac{dN_{total}}{dt } = \frac{dN_1}{dt} + \frac{dN_2}{dt}$ ------ (1)

here ;

$\frac{dN_{total}}{dt } = \lambda _{total} N_o$

Putting the values in (1);we have :

$- \lambda _{Total} N_o = - \lambda_e N_o + ( -\lambda r N_o})$

$\lambda _{Total} = \lambda_e + \lambda r$

As we also know that:

$\frac{1}{t_{1/2}} = \frac{[t_{1/2}]_{radiation}+[t_{1/2}]_{excretion}}{[t_{1/2}]_{radiation}*[t_{1/2}]_{excretion}}$

$\frac{1}{t_{1/2}}_{effective}} = \frac{[t_{1/2}]_{radiation}+[t_{1/2}]_{excretion}}{[t_{1/2}]_{radiation}*[t_{1/2}]_{excretion}}$

$\frac{1}{t_{1/2}}_{effective}} = \frac{9+6}{9*6}$

$\frac{1}{t_{1/2}_{effective}}}=\frac{15}{54}$

$t_{1/2}_{effective}} = \frac{54}{15}$

= 3.6 days

5 0

4 years ago

Read 2 more answers

What is velocity ratio?

STALIN [3.7K]

Explanation:

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__❎ NO SEX ❎ NO FLIRT❎__

⬇️⬇️⬇️⬇️Z000MM⬇️⬇️⬇️⬇️

373 629 9840

444000

4 0

3 years ago

Read 2 more answers

An alien spaceship 8x10^14m away sends us a radio wave signal. How long does it take for the signal to reach us?

Nata [24]

Time = distance/speed

Time = 8•10^14m / 3•10^8m/s

Time = about 2.7•10^6 seconds.
That's about 31 Earth days.

6 0

2 years ago

What is defined as the isolation and reduction of variables in an experiment in order to understand the impact of a specific var

ehidna [41]

aisnhsjdjxbxbxhxbxjx

7 0

3 years ago

A 31 kg block is initially at rest on a horizontal surface. A horizontal force of 83 N is required to set the block in motion. A

Hatshy [7]

Answer:

The static and kinetic coefficients of friction are 0.273 and 0.181, respectively.

Explanation:

By Newton's Laws of Motion and definition of maximum friction force, we derive the following two formulas for the static and kinetic coefficients of friction:

$\mu_{s} = \frac{f_{s}}{m\cdot g}$ (1)

$\mu_{k} = \frac{f_{k}}{m\cdot g}$ (2)

Where:

$\mu_{s}$ - Static coefficient of friction, no unit.

$\mu_{k}$ - Kinetic coefficient of friction, no unit.

$f_{s}$ - Static friction force, in newtons.

$f_{k}$ - Kinetic friction force, in newtons.

$m$ - Mass, in kilograms.

$g$ - Gravitational constant, in meters per square second.

If we know that $f_{s} = 83\,N$ , $f_{k} = 55\,N$ , $m = 31\,kg$ and $g = 9.807\,\frac{m}{s^{2}}$ , then the coefficients of friction are, respectively: