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3 years ago

Please please please help me

Physics

1 answer:

pogonyaev3 years ago

3 0

Answer:

C) seems to be the correct one

Each alpha particle emitted decreases the mass of the nucleus by 4 and decreases the atomic number by 2.

Also, each beta particle will increase the atomic number by 1.

So if C emits 5 alpha particles the atomic mass decreases by 20 and the atomic number decreases by 10. Then emission of 2 beta particles brings the atomic number up to minus 8.

So a total of 7 particles have been emitted and the number of alpha particles emitted exceeds the number of beta particles emitted.

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A ceiling fan with 90-cm-diameter blades is turning at 64 rpm . Suppose the fan coasts to a stop 28 s after being turned off. Wh

mixas84 [53]

Answer:

the speed of the tip of a blade 10 s after the fan is turned off is 16.889 m/s.

Explanation:

Given;

diameter of the ceiling fan, d = 90 cm = 0.9 m

angular speed of the fan, ω = 64 rpm

time taken for the fan to stop, t = 28 s

The distance traveled by the ceiling fan when it comes to a stop is calculated as;

$d = vt = \omega r\times t= ( \frac{64 \ rev}{\min} \times \frac{2 \pi \ rad}{rev} \times \frac{1 \min}{60 \ s} \times 0.9 \ m) \times 28 \ s\\\\d = 168.89 \ m$

The speed of the tip of a blade 10 s after the fan is turned off is calculated as;

$v = \frac{d}{t} \\\\v = \frac{168.89}{10} \\\\v = 16.889 \ m/s$

Therefore, the speed of the tip of a blade 10 s after the fan is turned off is 16.889 m/s.

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3 years ago

A stream moving with a speed of 7.1 m/s reaches a point where the cross-sectional area of the stream decreases to one half of th

lana66690 [7]

Answer:

14.2 m/s

Explanation:

Given data:

Speed of the stream, v₁ = 7.1 m/s

let the cross section area at initial point be A₁

now area at the second point, A₂ = (1/2)A₁ = 0.5A₁

now, from the continuity equation, we have

A₁v₁ = A₂v₂

where, v₂ is the velocity at the narrowed portion

thus, on substituting the values, we get

A₁ × 7.1 = 0.5A₁ × v₂

v₂ = 14.2 m/s

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