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Natasha2012 [34]
3 years ago
8

When exposed to a radioactive source which emits 1.2-MeV gamma-rays, a particular material is found to have a half-value thickne

ss X of 10 cm How thick would a shield made of this material need to be in order to block 75% of the radiation? A. 5 cm B. 20 cm C. 15 cm D. 25 cm E. 10 cm
Physics
1 answer:
iren2701 [21]3 years ago
4 0

Answer:E

Explanation:

It is given that Energy of gamma ray is E=1.2 Mev

Shielding effect can be measured by measuring the fraction of gamma rays blocked by shield. If certain thickness will able to block half the radiation then to block 75% radiation we need to add same amount of thickness in order to block the remaining radiation.

i.e. \frac{E}{2} fraction is blocked by 10 cm thickness

then remaining radiation is \frac{E}{2}

another 10 cm thickness will block the remaining half radiation i.e. \frac{1}{2}\times \frac{E}{2}=\frac{E}{4}

so total 75 % radiation will be blocked

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A 4 kg textbook sits on a desk. It is pushed horizontally with a 50 N applied force against a 15 N frictional force.
GarryVolchara [31]

a) See free-body diagram in attachment

b) The book is stationary in the vertical direction

c) The net horizontal force is 35 N in the forward direction

d) The net force on the book is 35 N in the forward horizontal direction

e) The acceleration is 8.75 m/s^2 in the forward direction

Explanation:

a)

The free-body diagram of a body represents all the forces acting on the body using arrows, where the length of each arrow is proportional to the magnitude of the force and points in the same direction.

From the diagram of this book, we see there are 4 forces acting on the book:

- The applied force, F = 50 N, pushing forward in the horizontal direction

- The frictional force, F_f = 15 N, pulling backward in the horizontal direction (the frictional force always acts in the direction opposite to the motion)

- The weight of the book, W=mg, where m is the mass of the book and g=9.8 m/s^2 is the acceleration of gravity, acting downward. We can calculate its magnitude using the mass of the book, m = 4 kg:

W=(4)(9.8)=39.2 N

- The normal reaction exerted by the desk on the book, N, acting upward, and balancing the weight of the book

b)

The book is in equilibrium in the vertical direction, therefore there is no motion.

In fact, the magnitude of the normal reaction (N) exerted by the desk on the book is exactly equal to the weight of the book (W), so the equation of motion along the vertical direction is

N-W=ma

where a is the acceleration; however, since N = W, this becomes

a=0

And since the book is initially at rest on the desk, this means that there is no motion.

c)

We said there are two forces acting in the horizontal direction:

- The applied force, F = 50 N, forward

- The frictional force, F_f = 15 N, backward

Since they act along the same line, we can calculate their resultant as

\sum F = F - F_f = 50 - 15 = 35 N

and therefore the net force is 35 N in the forward direction.

d)

The net force is obtained as the resultant  of the net forces in the horizontal and vertical direction. However, we have:

- The net force in the horizontal direction is 35 N

- The net force in the vertical direction is zero, because the weight is balanced by the normal reaction

Therefore, this means that the total net force acting on the book is just the net force acting on the horizontal direction, so 35 N forward.

e)

The acceleration of the book can be calculated by using Newton's second law:

\sum F = ma

where

\sum F is the net force

m is the mass

a is the acceleration

Here we have:

\sum F = 35 N (in the forward direction)

m = 4 kg

Therefore, the acceleration is

a=\frac{\sum F}{m}=\frac{35}{4}=8.75 m/s^2 (forward)

Learn more about forces, weight and Newton's second law:

brainly.com/question/8459017

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#LearnwithBrainly

8 0
3 years ago
Does Solid surfaces reflect better than liquid surfaces? If why?
zloy xaker [14]
It depends on what type of solid
7 0
3 years ago
During convection, heat warms up a fluid, making the fluid less dense so it begins to RISE. As the warm fluid moves, it begins t
Fiesta28 [93]

Answer:

True

Explanation:

Convection is a form of heat transfer that is predominantly common in fluids especially liquid and gas.

It occurs by the movement of a part of substance from one place to another based on density and temperature differences.

A typical convection cell is made up of a liquid that is heated. The liquid part close to the heat source becomes warmer and rises due to its low density. The part away from the heat source is more dense and begins to sink.

This analogy is commonly demonstrated in a boiling pot of water.

7 0
3 years ago
Read 2 more answers
1. Earth releases about 44-46 Tw of heat, in fact heat can be converted into
Aleksandr [31]

Answer:

  even if it all could be used, it wouldn't be enough

Explanation:

The land area of the US is about 5.45% of the world's area, so the amount of released heat over the area of the US is on the order of 2.4 Tw. Current technology for converting geothermal energy to electricity is about 12% efficient, so the available energy might amount to 0.29 Tw if it could all be captured.

Energy consumption in the US in 2019 was on the order of 0.46 Tw. This suggests that even if <em>all</em> of the thermal energy radiated by the Earth from the US could be turned to useful forms of energy, it would meet only about 60% of the US need for energy.

8 0
3 years ago
A trampoline spring has a force constant k = 800 N/m and is stretched exactly 17.5cm. What is the energy required to do this?
Artist 52 [7]

Answer:

the energy required for the extension is 12.25 J

Explanation:

Given;

force constant of trampoline spring, k = 800 N/m

extension of trampoline spring, x = 17.5 cm = 0.175 m

The energy required for the extension is calculated as;

E = ¹/₂kx²

E = 0.5 x 800 x 0.175²

E = 12.25 J

Therefore, the energy required for the extension is 12.25 J

6 0
3 years ago
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