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katrin [286]
2 years ago
4

A sample of radioactive waste has a half-life of 10 years and an activity level of 2 curies. After how many years will the activ

ity level of this sample be 0.25 curie?
Physics
1 answer:
nasty-shy [4]2 years ago
8 0
A sample of radioactive waste has a half-life of 10 years and an activity level of 2 curies. After how many years will the activity level of this sample be 0.25 curie?

Your answer is: 30 years
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A physical change occurs when a material changes shape or size but the composition of the material does not change. True or Fals
Elden [556K]
It is true that a physical change occurs when a material changes shape or size, but the composition of the material does not change. The correct answer is True. 
6 0
2 years ago
To prevent collisions and violations at intersections that have traffic signals, use the _____ to ensure the intersection is cle
Ann [662]
The answer should be:
<span>To prevent collisions and violations at intersections that have traffic signals, use the d</span>elayed acceleration technique<span> to ensure the intersection is clear before you enter it.
Delayed acceleration technique refers to w</span><span>aiting to go through an intersection until you have a chance to scan for other vehicles.</span>
3 0
2 years ago
A point charge Q is held at a distance r from the center of a dipole that consists of two charges ±qseparated by a distance s. T
atroni [7]

Answer:

The magnitude of the force on the dipole due to the charge Q = \rm \dfrac{1}{\epsilon_o}\times \dfrac{1}{4\pi }\dfrac{2qQs}{r^3}.

The magnitude of the torque on the dipole = \rm \dfrac{1}{\epsilon_o}\times \dfrac{1}{4\pi}\dfrac{2qQs^2}{r^3}.

Explanation:

Given that a point charge Q is held at a distance r from the center of a dipole that consists of two charges ±q, separated by a distance s and the charge Q is located in the plane that bisects the dipole.

The magnitude of the electric field that the dipole exerts at the position where the charge Q is held is given by

\rm E = \dfrac{k2qs}{(r^2+s^2)^{3/2}}.

<em>where</em>,

k is the Coulomb's constant, having value = \dfrac{1}{4\pi \epsilon_o}

\epsilon_o is the electrical permittivity of free space.

Also, r>>s, therefore, \rm r^2+s^2\approx r^2.

\rm E = \dfrac{k2qs}{(r^2)^{3/2}}=\dfrac{k2qs}{r^3}.

The magnitude of the electric force F on a charge q placed at a point and the magnitude of the electric field E at that point are related as

\rm F=qE

Therefore, the electric force on the charge Q due to the dipole is given by

\rm F=Q\dfrac{k2qs}{r^3}=\dfrac{1}{4\pi \epsilon_o}\dfrac{2qQs}{r^3}.

According to Newton's third law of motion, the magnitude of the force exerted by the dipole on the charge Q is same as the magnitude of the force exerted by the charge on the dipole.

Thus, the magnitude of the force on the dipole due to the charge Q = \dfrac{1}{\epsilon_o}\times \dfrac{1}{4\pi }\dfrac{2qQs}{r^3}.

The magnitude of the torque on the dipole is given by

\rm \tau = Fs\ \sin\theta

Since the charge Q is placed in the plane that bisects the dipole, therefore, \theta = 90^\circ.

\rm \tau = \dfrac{1}{4\pi \epsilon_o}\dfrac{2qQs}{r^3}\cdot s\cdot 1=\dfrac{1}{4\pi \epsilon_o}\dfrac{2qQs^2}{r^3}.

4 0
2 years ago
A certain humidifier operates by raising water to the boiling point and then evaporating it. Every minute 30 g of water at 20◦ C
Sveta_85 [38]

Answer:

The value of total energy needed per minute for the humidifier = 77.78 KJ

Explanation:

Total energy per minute the humidifier required = Energy required to heat water to boiling point) + Energy required to convert liquid water into vapor at the boiling point) ----- (1)

Specific heat of water = 4190 \frac{J}{kg k}

The heat of vaporization is =  2256 \frac{KJ}{kg}

Mass = 0.030 kg

Energy needed to heat water to boiling point =  m c ( T_{2} - T_{1} )

Energy needed to heat water to boiling point = 0.030 × 4.19 × (100 - 20)

Energy (E_{1}) = 10.08 KJ

Energy needed to convert liquid water into vapor at the boiling point

E_{2} = 0.030 × 2256 = 67.68 KJ

Thus the total energy needed E =  E_{1} + E_{2}

E = 10.08 + 67.68

E = 77.78 KJ

This is the value of total energy needed per minute for the humidifier.

9 0
2 years ago
An electron and a proton, starting from rest, are accelerated through an electric potential difference of the same magnitude. in
Yakvenalex [24]
The charges are the same in absolute value, so the change of potential energy is the same. That means that the change in kinetic energy is also the same. Then:

1 = Ke/Kp = m_e *v_e^2 / m_p * v_p^2, or

v_e/v_p = sqrt( m_p/m_e),

So the speed of the electron will be sqrt( m_p/m_e) times greater than the speed of the proton
4 0
2 years ago
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