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alexgriva [62]
3 years ago
14

If you have 80g of a radioactive substance whose half life is 2 days, how long will it take for the substance to decay to the po

int where there is only 10g left?
Physics
1 answer:
Ber [7]3 years ago
5 0

Answer:

6 days.

Explanation:

From radioactivity, The expression for half life is given as,

R/R' = 2⁽ᵃ/ᵇ)................... Equation 1

Where R = original mass of the radioactive substance, R' = Remaining mass of the radioactive substance after decay, a = Total time taken to decay, b = half life.

Given: R = 80 g, R' = 10 g, b = 2 days.

Substitute into equation 1

80/10 = 2⁽ᵃ/²⁾

8 = 2⁽ᵃ/²⁾

2³ = 2⁽ᵃ/²)

Equating the base and solving for a

3 = a/2

a = 2×3

a = 6 days.

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A car goes around a curve of radius r at a constant speed v. Then it goes around a curve ofradius 2r at speed 2v. What is the ce
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The centripetal force on the car as it goes around the second curve is twice that compared to the first.

What is Centripetal force?

It is the force that is necessary to keep an object moving in a curved path and that is directed inward toward the center of rotation.

The formula of Centripetal force is:

F(c) = (m* v^2) / r

Here,

At the first curve,

The curve of radius = r

The constant speed = v

At the second curve,

The car speed (v')= 2 v

The radius of the curve (r')=2 r

According to the formula of centripetal Force:

As the car goes around the second curve,

F'(c) = m*v'^2 / r'

F'(c) = m* (2*v)^2 / 2r

F'(c) = 2* F

Thus,

The centripetal force on the car as it goes around the second curve is twice that compared to the first.

Learn more about centripetal force here:

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8 0
1 year ago
In Ch. 1.6, the authors point out that interstellar space is not actually as empty as it seems. There is actually a lot of diffu
wel

Answer:

very small solid particles called interstellar dust.

Explanation:

In the space between the stars there is gas and dust, which represent at least 20% of the mass of our galaxy. In the Milky Way it is considered that there is a gas density of approximately 0.2 to 0.5 atoms / cm3 in the surroundings of the Sun; with respect to the dust an average of 1 g / cm3 is estimated.

Gas is about atoms and molecules, mainly hydrogen; In order of abundance, helium, carbon, oxygen, nitrogen and iron follow. On the other hand, the dust is tiny particles, generally smaller than 10 microns; the dust does not shine and therefore it is only distinguished when it is projected on bright regions (nebulae or clusters).

Interstellar matter is mainly concentrated towards the plane of the galaxy, in the strip corresponding to the Milky Way; there you can see bright nebulas of diffuse character called nebulas. These nebulae are classified according to three types: (a) bright or emission nebulae, (b) reflection nebulae and (c) planetary nebulae.

Hydrogen appears both ionized and neutral; The bright nebulae are composed of ionized hydrogen and other ionized elements. Non-ionized (neutral) hydrogen is found in the spiral arms of the Milky Way and can be detected through radio waves.

6 0
3 years ago
When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time o
dsp73

Answer:

c. about 1/10 as great.

Explanation:

While jumping form a certain height when we bend our knees upon reaching  the ground such that the time taken to come to complete rest is increased by 10 times then the impact force gets reduced to one-tenth of the initial value when we would not do so.

This is in accordance with the Newton's second law of motion which states that the rate of change in velocity is directly proportional to the force applied on the body.

Mathematically:

F\propto\frac{d}{dt} (p)

\Rightarrow F=\frac{d}{dt} (m.v)

since mass is constant

F=m\frac{d}{dt}v

when dt=10t

then,

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F'=\frac{1}{10} \times \frac{m.v}{t}

F'=\frac{F}{10} the body will experience the tenth part of the maximum force.

where:

\frac{d}{dt} = represents the rate of change in dependent quantity with respect to time

p= momentum

m= mass of the person jumping

v= velocity of the body while hitting the ground.

7 0
3 years ago
In middle ages people believed that abnormal behavior was cause by ?
Svetach [21]
C, they didn't know any better
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3 years ago
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attashe74 [19]

Answer:

We feel cold when tap or well water in winter because heat flows from hot body to cold body.

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2 years ago
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