Ask question

Ask question

All categories

3 years ago

10

Why does the sun appear to move across the sky over the course of the day? A. because the sun revolves around Earth B. because E

arth revolves around the sun C. because the sun rotates on its axis D. because Earth rotates on its axis. PLease answer quickly next question is 50 points

2 answers:

aev [14]3 years ago

6 0

Pretty sure it's:
D. Earth rotates on its axis

bagirrra123 [75]3 years ago

3 0

Answer:

i would say B

Explanation:

You might be interested in

A thin rod of length 0.79 m and mass 130 g is suspended freely from one end. It is pulled to one side and then allowed to swing

-Dominant- [34]

Answer:

a) 0.3965 j

b) 0.3112 m

Explanation:

The picture attached explains it all. Thank you

3 0

3 years ago

Why is honesty especially important in a scientist when the results of an experiment go against predictions❓❔

kramer

Because other scientists and science in general rely on their collegues' research which in turn allows development of our knowledge on the given subject. The more dont-to-earth reason may be safety. If someone performs an experiment without knowledge of its true results it might result in some danger to the safety of those perforning it without knowledge of all the risks.

8 0

3 years ago

A steel wire of length 31.0 m and a copper wire of length 17.0 m, both with 1.00-mm diameters, are connected end to end and stre

Brut [27]

Answer:

The time taken is $t = 0.356 \ s$

Explanation:

From the question we are told that

The length of steel the wire is $l_1 = 31.0 \ m$

The length of the copper wire is $l_2 = 17.0 \ m$

The diameter of the wire is $d = 1.00 \ m = 1.0 *10^{-3} \ m$

The tension is $T = 122 \ N$

The time taken by the transverse wave to travel the length of the two wire is mathematically represented as

$t = t_s + t_c$

Where $t_s$ is the time taken to transverse the steel wire which is mathematically represented as

$t_s = l_1 * [ \sqrt{ \frac{\rho * \pi * d^2 }{ 4 * T} } ]$

here $\rho_s$ is the density of steel with a value $\rho_s = 8920 \ kg/m^3$

So

$t_s = 31 * [ \sqrt{ \frac{8920 * 3.142* (1*10^{-3})^2 }{ 4 * 122} } ]$

$t_s = 0.235 \ s$

And

$t_c$ is the time taken to transverse the copper wire which is mathematically represented as

$t_c = l_2 * [ \sqrt{ \frac{\rho_c * \pi * d^2 }{ 4 * T} } ]$

here $\rho_c$ is the density of steel with a value $\rho_s = 7860 \ kg/m^3$

So

$t_c = 17 * [ \sqrt{ \frac{7860 * 3.142* (1*10^{-3})^2 }{ 4 * 122} } ]$

$t_c =0.121$

So

$t = t_c + t_s$

$t = 0.121 + 0.235$

$t = 0.356 \ s$

4 0

3 years ago

A 100 V battery is connected across a

Sergio039 [100]

1 mA = 0.001 A

Therefore, 5 mA = 0.001 * 5

=0.005 A

Resistance = voltage / current

= 100 / 0.005

= 20000 ohms

Current = voltage / resistance

= 25 / 20000

= 0.00125 A (or) 1.25 mA

5 0

3 years ago

1.A river flowing steadily at a rate of 240 m3/s is considered for hydroelectric power generation. It is determined that a dam c

SIZIF [17.4K]

Answer:

the power that can be generated by the river is 117.6 MW

Explanation:

Given that;

Volume flow rate of river v = 240 m³/s

Height above the lake surface a h = 50 m

Amount of power can be generated from this river water after the dam is filled = ?

Now the collected water in the dam contains potential energy which is used for the power generation,

hence, total mechanical energy is due to potential energy alone.

$E_{mech}$ = m(gh)

first we determine the mass flow rate of the fluid m

m = p×v

where p is density ( 1000 kg/m³

so we substitute

m = 1000kg/m³ × 240 m³/s

m = 240000 kg/s

so we plug in our values into ( $E_{mech}$ = m(gh) kJ/kg )

$E_{mech}$ = 240000 × 9.8 × 50

$E_{mech}$ = 117600000 W

$E_{mech}$ = 117.6 MW

Therefore, the power that can be generated by the river is 117.6 MW

4 0

3 years ago