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andrew-mc [135]
2 years ago
10

If the activity of a radionuclide decreases from 5,000 disintegrations per minute to 625 disintegrations per minute

Physics
1 answer:
lys-0071 [83]2 years ago
7 0

Answer:

4 hrs

Explanation:

625 = 5000 (1/2)^n

625/5000 = 1/2^n

n = 3 half lives

3 half lives = 12 hours       1 half life = 4 hrs

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3 years ago
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A block weighing 400 kg rests on a horizontal surface and supports on top of it ,another block of weight 100 kg which is attache
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Answer:

F_a=1470\ N

Explanation:

<u>Friction Force</u>

When objects are in contact with other objects or rough surfaces, the friction forces appear when we try to move them with respect to each other. The friction forces always have a direction opposite to the intended motion, i.e. if the object is pushed to the right, the friction force is exerted to the left.

There are two blocks, one of 400 kg on a horizontal surface and other of 100 kg on top of it tied to a vertical wall by a string. If we try to push the first block, it will not move freely, because two friction forces appear: one exerted by the surface and the other exerted by the contact between both blocks. Let's call them Fr1 and Fr2 respectively. The block 2 is attached to the wall by a string, so it won't simply move with the block 1.  

Please find the free body diagrams in the figure provided below.

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\displaystyle F_a-F_{r1}-F_{r2}=m.a=0

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\displaystyle F_a=F_{r1}+F_{r2}.....[1]

The mass 2 is tried to be pushed to the right by the friction force Fr2 between them, but the string keeps it fixed in position with the tension T. The equation in the horizontal axis is

\displaystyle F_{r2}-T=0

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Replacing in [1]

\displaystyle F_{a}=\mu \ m_2\ g\ +\mu(m_1+m_2)g

Simplifying

\displaystyle F_{a}=\mu \ g(m_1+2\ m_2)

Plugging in the values

\displaystyle F_{a}=0.25(9.8)[400+2(100)]

\boxed{F_a=1470\ N}

8 0
3 years ago
You can use any coordinate system you like in order to solve a projectile motion problem. To demonstrate the truth of this state
posledela

Answer:

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