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vladimir2022 [97]

3 years ago

11

Two cars are travelling in the same direction on a road. The blue car is travelling at 50 m/s in front of the red car, which is

travelling at 75 m/s. What is their relative speed? *

1 answer:

Anestetic [448]3 years ago

6 0

Explanation:

The speed of the red car, relative to the blue car, is:

v = 75 m/s − 50 m/s

v = 25 m/s

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A radioactive material has a count rate of 400 per minute. It has a half life of 40 years. How long will it take to decay to a r

cestrela7 [59]

Answer:

160 years.

Explanation:

From the question given above, the following data were obtained:

Initial count rate (Cᵢ) = 400 count/min

Half-life (t½) = 40 years

Final count rate (Cբ) = 25 count/min

Time (t) =?

Next, we shall determine the number of half-lives that has elapse. This can be obtained as follow:

Initial count rate (Cᵢ) = 400 count/min

Final count rate (Cբ) = 25 count/min

Number of half-lives (n) =?

Cբ = 1/2ⁿ × Cᵢ

25 = 1/2ⁿ × 400

Cross multiply

25 × 2ⁿ = 400

Divide both side by 25

2ⁿ = 400/25

2ⁿ = 16

Express 16 in index form with 2 as the base

2ⁿ = 2⁴

n = 4

Thus, 4 half-lives has elapsed.

Finally, we shall determine the time taken for the radioactive material to decay to the rate of 25 counts per minute. This can be obtained as follow:

Half-life (t½) = 40 years

Number of half-lives (n) = 4

Time (t) =?

n = t / t½

4 = t / 40

Cross multiply

t = 4 × 40

t = 160 years.

Thus, it will take 160 years for the radioactive material to decay to the rate of 25 counts per minute.

7 0

3 years ago

Assume that the polymer material has a constant refractive index of 1.5. For light of 600nm wavelength at normal incidence, what

yaroslaw [1]

Answer:

Minimum thickness will be 100 nm

Explanation:

We have given refractive index is n = 1.5

Wavelength of the light incidence $\lambda$ = 600 nm

We have to find the smallest thickness of the film so that there will be minimum light reflect

For minimum thickness of non reflecting film

$t=\frac{\lambda }{4n}$ , here t is thickness, $\lambda$ is wavelength and n is refractive index

Putting all values $t=\frac{600}{4\times 1.5}=100nm$

So minimum thickness will be 100 nm

8 0

3 years ago

In what way are all sounds alike?

Anna35 [415]

Answer:

D. all sounds are caused by vibrations

Explanation:

5 0

3 years ago

An 8.00- W resistor is dissipating 100 watts. What are the current through it and the difference of potential across it?

hjlf

Answer:

I= 3.5 amps

Explanation:

Step one:

given data

rating of resistor R= 8 ohms

power P= 100W

Required

The current I

Step two

Yet this power is also given by

$P = I^2R$

make I subject of the formula we have

$I= \sqrt{\frac{P}{R} }$

substitute

$I= \sqrt{\frac{100}{8} }\\\\I=\sqrt{12.5}\\\\I= 3.5 amps$

8 0

3 years ago

If a reaction starts with 30 grams how many should it end with ?

zysi [14]

30grams

Explanation:

If a reaction starts with 30grams then the reaction should end with 30grams.

This in conformity with the law of conservation of mass.

The law states that "in an isolated system, mass is neither created nor destroyed during chemical transformation".
Mass is the quantity of matter contained in a substance.
In chemical reactions, the mass of reactants must always be the same with the mass of the product baring any loss.
In an isolated system, there is no exchange of energy and mass.
Chemical systems are usually treated as isolated systems in which mass is conserved.

Learn more:

Chemical laws brainly.com/question/5896850

#learnwithBrainly

4 0

3 years ago