Anyone knows this please help me

PLEASE HELP. A substance decays according the the equation ae^-0.0025t, where t is in minutes. Find the half life of the substan

mojhsa [17]

First of all, that's not an equation. An equation needs an 'equals' sign ( = ),
so you need something like

   Amount present = a e^-0.0025t .

   'a' = amount present when t = 0 .

The half-life is the time it takes for the original amount to decay to half of it.

That's just 't' when       e^-0.0025t = 1/2

Take the natural log of each side: -0.0025t = ln(0.5)

Divide each side by -0.0025 : t = ln(0.5) / (-0.0025) =

   (-0.69315) / (-0.0025) =

   <em>t = 277.26 minutes</em>

( 4hrs 37min 15.5sec)

Rounded to nearest tenth: t = 277.3 minutes .

3 0

4 years ago

Calculate the minimum wavelength (λ0) for the continuous spectrum of X-rays emitted when.. a) 30-kV electrons strike a cobalt (C

Sholpan [36]

Explanation:

The relationship between the wavelength and the potential difference V is given by :

$\lambda=\dfrac{h}{\sqrt{2me}}\times \dfrac{1}{\sqrt{V}}$

Putting the values of known parameters,

$\lambda=\dfrac{12.28}{\sqrt{V} }\times 10^{-10}\ m$

(a) $V=30\ kV=30000\ V$

$\lambda=\dfrac{12.28}{\sqrt{30000} }\times 10^{-10}\ m$

$\lambda=7.08\times 10^{-12}\ m$

(b) $V=60\ kV=60000\ V$

$\lambda=\dfrac{12.28}{\sqrt{60000} }\times 10^{-10}\ m$

$\lambda=5.01\times 10^{-12}\ m$

Hence, this is the required solution.

4 0

4 years ago

A light bulb has a power rating of 60 W. What is the current running into it if it is plugged into a 120 V outlet?

kifflom [539]

Answer:

0.5 Amperes

Explanation:

Information that we have:

Power: $P=60W$

Voltage: $V=120V$

and we use the equation that relates this two quantities to the Current (I):

$I=\frac{P}{V}$

where I is the curent, P is the Power and V is the Voltage.

we substitute the values given for the Power and the Voltage to find the current:

$I=\frac{60W}{120V}\\ I=0.5A$

the Current running into the bulb is 0.5 Amperes

3 0

3 years ago

Figure one, voltmeters

slava [35]

Answer:

(i) Half

(ii) 3 V

(iii) V₁

Explanation:

(i) The given parameters are;

The circuits have identical resistances

The number of resistors in circuit 1 = 1 resistor

The number of resistors in circuit 2 = 2 resistors

Let 'R' represent the value of each resistor, we have;

The total resistance of circuit 1 = R Ohm

The total resistance of circuit 3 = 2·R Ohm

∴ The total resistance of circuit 1 = (1/2) × The total resistance of circuit 3

∴ The resistance of circuit 1 is <u>half</u> the resistance of circuit 3

(ii) The potential difference of each cell, V = 1.5 volts

The number of cells in circuit 2 = 2 cells

The total potential difference of the cells of circuit 2 = 2 × 1.5 volts = 3 × volts = 3 V.

The voltmeter reading = The potential difference across the cell or cells it is applied

∴ The voltmeter reading on voltmeter, V₂, applied across the cells of circuit 2 = 3 V

(iii) The voltmeter reading V₁ = 1.5 V

The voltmeter reading V₂ = 3 V

The voltmeter reading V₃ = 4.5/(2·R) × R = 2.25 V

Therefore, the voltmeter reading with the smallest volt, is V₁ = 1.5 V

6 0

3 years ago

a couple has just learned that their daughter has hemophilia. They already have a son who does not have the disease. What are th

Step2247 [10]

Answer: The genotypes of the couple are- XᵇX and XᵇY, where Xᵇ denotes the X chromosome having gene for hemophilia.

Hemophilia is a X linked recessive disorder, which means that the gene for hemophilia is carried by X chromosome. A female individual will be affected by the disorder if she carries two copies of the gene causing hemophilia. A male ( XY) will be hemophilic when his X chromosome bears the gene for hemophilia.

As per the information given in the question, son is not having the disease, which means that he has inherited normal X chromosome from his mother. On the other hand, daughter is hemophilic, which indicates that she has inherited both the X chromosomes with hemophilic gene that is XᵇXᵇ ( one X from father and other from mother).

This condition is only possible when the male parent is affected and female parent is carrier for the disease.

Thus, the genotypes of the couple are- XᵇX and XᵇY, where Xᵇ denotes the X chromosome having gene for hemophilia.

3 0

4 years ago