Betelgeuse has been labeled as a Variant Star, which means that its brightness can fluctuate over the course of years, this has made difficult for astronomers to measure the exact distance of the star. Right now the star is estimated to be around 613 and 881ly away from earth, although, for the sake of your second question, we will take 640 years as our estimated value.

In 1380 (640 years ago) the Battle of Kulikovo took place. A battle of remarkable importance to Russian history, in which the Russian army, led by Prince Dmitry of Moscow, defeated the Mongol army, defining a turning point in the Mongol dominance, and setting the bases for what Russia is today.

6 0

3 years ago

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Coal is how much worse than natural gas when it comes to carbon dioxide emissions?

Naya [18.7K]

Answer:

True

Explanation:

Its worse

4 0

3 years ago

A beaker of mass 1.3 kg containing 2.8 kg of water rests on a scale. A 3.7 kg block of a metallic alloy of density 4600 kg/m3 is

Oksana_A [137]

1) Force read on the upper scale: 33.4 N

2) Force read on the lower scale: 43.0 N

Explanation:

The reading on the upper scale is equal to the net force acting on the block of metallic alloy. The net force is given by:

$F=W-B$ (1)

where

W is the weight of the block (downward)

B is the buoyant force (upward)

The weight of the block is given by

$W=mg$

where m = 3.7 kg is the mass of the block and $g=9.8 m/s^2$ is the acceleration of gravity.

The buoyant force is given by

$B=\rho_w V g$

where

$\rho_w=1000 kg/m^3$ is the water density

V is the volume of the block

The volume of the block can be written as

$V=\frac{m}{\rho_b}$

where $\rho_b=4600 kg/m^3$ is the density of the block.

Substituting everything into eq.(1), we find:

$F=mg-\rho_w \frac{m}{\rho_b}g=(3.7)(9.8)-(1000)\frac{1.3}{4600}(9.8)=33.4 N$

Here we want to find the force on the lower scale.

The force on the lower scale is equal to the difference between the total weight of the system (given by the weight of the beaker + the weight of the water + the weight of the block) and the upper net force exerted on the upper scale, therefore:

$F' = m_B g + m_wg+m_b g - F$