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3 years ago

Please help me

Physics

1 answer:

g100num [7]3 years ago

5 0

Answer:

0.3956

Explanation:

Newton's 2nd law of motion says that Force = Mass*Acceleration (f=ma) so to find the force used on the football you multiply it's mass by its acceleration.

0.43*0.92 = 0.3956.

0.4 if you round

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The spectrum of a distant star shows that one in 2 e6 of the atoms of a particular element is in its first excited state 7.5 eV

Alchen [17]

Answer:

The temperature of star is 5473.87 K

Explanation:

Given:

Energy difference $\Delta E = 7.5$ eV

The ratio of number of particle $\frac{N_{f} }{N_{i} } = \frac{1}{2 \times 10^{6} }$

Degeneracy ratio $\frac{g_{f} }{g_{i} } = 4$

From the formula of boltzmann distribution for population levels,

$\frac{N_{f} }{N_{i} } =\frac{g_{f} }{g_{i} } e^{-\frac{\Delta E}{kT} }$

Where $k =$ boltzmann constant = $8.62 \times 10^{-5} \frac{eV}{K}$

$\frac{1}{2 \times 10^{6} } =4 e^{-\frac{7.5 eV}{8.62 \times 10^{-5} T} }$

$8 \times 10^{6} } = e^{\frac{7.5 eV}{8.62 \times 10^{-5} T} }$

$\ln(8 \times 10^{6}) = {\frac{7.5 eV}{8.62 \times 10^{-5} T} }$

$T = {\frac{7.5 eV}{8.62 \times 10^{-5} \ln(8 \times 10^{6})} }$

$T = 5473.87$ K

Therefore, the temperature of star is 5473.87 K

5 0

3 years ago

. How much work in joules is done by a person who uses a force of 25 N to move a desk 3.0 m?

sergejj [24]

We Know, W = F * s
here, F = 25 N
s = 3 m

Substitute it into the expression,
W = 25 * 3
W = 75 Joule

So, your final answer is 75 J

Hope this helps!

7 0

3 years ago

A net force of 200 newtons is applied to a wagon for 3 seconds. This cause the wagons to undergo a change in momentum of ?

suter [353]

Physics- damon, Monday, December 1, 2014 at 3:27 pm force =change in momentum\ change in time or m a if m is constant

change in momentum/3=200

change in momentum =3*200 kg m/s

8 0

3 years ago

2. A can filled with sand has a mass of 0.65kg is swung overhead in a horizontal circle of radius 0.70m at a constant rate of 2.

Aliun [14]

<h3><u>Answer</u>;</h3>

≈ 5 Kgm²/sec

<h3><u>Explanation</u>;</h3>

Angular momentum is given by the formula

L = Iω, where I is the moment of inertia and ω is the angular speed.

I = mr², where m is the mass and r is the radius

= 0.65 × 0.7²

= 0.3185

Angular speed, ω = v/r

= (2 × 3.142 × r × 2.5) r

= 15.71

Therefore;

Angular momentum = Iω

= 0.3185 × 15.71

= 5.003635

<u>≈ 5 Kgm²/sec</u>

6 0

2 years ago

What material parameters determine resistivity?

sleet_krkn [62]

Answer:

Resistivity $\rho =\frac{RA}{l}$

It depends upon cross sectional area and length of material

Explanation:

The resistance of any material is given by $R=\frac{\rho l}{A}$ , here $\rho$ is the resistivity of material , l is length of material and A is cross sectional area

So resistivity $\rho =\frac{RA}{l}$

So resistuivity of any material depends upon area of cross section and length of material

If cross sectional area will be more then resistivity will be more. And is length of the material will be more then resistivity will be less

3 0

2 years ago