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amid [387]
3 years ago
11

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

ate of 25 counts per minute
Physics
1 answer:
cestrela7 [59]3 years ago
7 0

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.

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Maureen is training for a backpacking trip. Which of the following training plans follows the FITT
lawyer [7]

Answer:

The answer is "Walk three days a week, gradually adding distance and hills."

Explanation:

The FITT Principle <u>guides a person in becoming a fitter version of himself by following a particular frequency, intensity, time and type of exercise in order to achieve his goals.</u>

<u>Frequency</u>- this refers to how often a person should do an exercise. For example, 5 times a week of intense core workout.

<u>Intensity</u>- this refers to the person's vigour or strength in doing the workout. This depends whether the person is doing a high-intensity or a low-intensity exercise.

<u>Time</u>- this refers to the length of a person's exercise. This will largely depend on every individual's fitness level.

<u>Type of Exercise</u>- this refers to the exercise that a person should incorporate in his training<u> in order to avoid injuries of using the same muscles over and over again.</u>

Among the choices above, it is only the second choice (Walk three days a week, gradually adding distance and hills) that follows the FITT principle. Walking shouldn't be kept at the same pace and distance for many weeks, since it results to<em> boredom and overuse injuries. </em>This will also lead to a plateau when it comes to people who are trying to lose weight because the body has already well-adjusted to the exercise and cannot be challenged anymore.

<em>Gradually increasing the distance and hills will allow the person to be more challenged </em>and<em> </em>will also increase his desire to workout (because he is seeing results).

6 0
3 years ago
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liq [111]
It means that the soccer ball is a soccer ball bc it’s a soccer ball yk ?
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A long wire carrying a 5.0 A current perpendicular to the (xy)-plane intersects the x-axis at x = -2.00 cm. A second parallel wi
zimovet [89]

Answer:

a. 05cm from x axis

b. 8cm from x axis

Explanation:

If the net magnetic field is zero and the currents are in the same direction then the thanks point is between the currents i1 and i2 as show in the attachment below

a. Given that i1= 5A and i2=3A

Let assume the null point is xcm from current i1, then the null point will be (4-x)cm from current i2 since the total length is 4cm.

Now the magnetic field of the current i1 from the null point= to magnetic field of current i2 from the null point

B1=B2

μi1/2πx=μi2/2π(4-x)

i1/x=i2/(4-x)

5/x=3/(4-x)

20-5x=3x

8x=20

8x=2.5cm

since from the left of x axis is 2cm, then the null point is 2.5-2 which 0.5cm from the origin x axis.

The null point is 0.5cm from the origin x axis

b. If both current are flowing in opposite direction, the null point lies outside of the current.

Then with same analysis let assume the first current i1 is xcm from the null point and since the total length is 4cm the second current i2 will be (x-4)cm from the null point.

Also the magnetic field of the current i1 from the null point = to magnetic field of current i2 from the null point

B1=B2

μi1/2πx=μi2/2π(x-4)

i1/x=i2/(x-4)

5/x=3/(x-4)

5x-20=3x

2x=20

x=10cm.

This shows that the distance of the null point from current i1 is 10cm and the current i1 is 2cm from the x axis, then the null point is 10-2=8cm from the origin x axis.

The null point is 8cm from the x axis.

Check the attachment to see the diagram of the current and the null points

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Describe how positive and negatives pairs will react?
oksian1 [2.3K]
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Annette [7]

Answer:

option (D)

Explanation:

Here initial rotation speed is given, final rotation speed is given and asking for time.

If we use

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For this equation, we don't have any information about the value of angular displacement and angular acceleration, so it is not useful.

B) ω=ω0+αt

For this equation, we don't have any information about angular acceleration, so it is not useful.

C) ω2=ω02+2α(θ−θ0)

In this equation, time is not included, so it is not useful.

D) So, more information is needed.

Thus, option (D) is true.

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