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3 years ago

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I have a doubt on heat and temperature. I need help with this science question and here the question: The water in a lake just r

eached freezing point temperature. Why can’t you go ice skating on it yet?

1 answer:

Volgvan3 years ago

5 0

Answer:

you can't go ice skating on it because if it just reached the temp then you need to wait for about 2 hours

Explanation:

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A ball is thrown vertically upwards with an initial velocity of 20.00 m/s. Neglecting air resistance, how long is the ball in th

algol [13]

Answer:

1) The greatest height attained by the ball equals 20.387 meters.

2) The time it takes for the ball to reach 15 meters approximately equals 1 second.

Explanation:

The greatest height will be attained when the ball stop's in the air and starts falling back to the earth.

thus using third equation of kinematics we obtain the height attained as

$v^2=u^2+2as$

where

'v' is the final speed of the ball

'u' is the initial speed of the ball

'a' is the acceleration that the ball is under which in this case equals 9.81 $m/s^{2}$

's' is the distance it covers

Thus for maximum height applying the values in the equation we get

$0=20^{2}-2\times 9.81\times h\\\\\therefore h=\frac{20^{2}}{2\times 9.81}=20.387meters$

Using the same equation we can find the speed of the ball when it reaches 15 meters of height as

$v^2=20^{2}-2\times 9.81\times 15\\\\v^{2}=105.7\\\\\therefore v=10.28m/s$

the time it takes to reduce the velocity to this value can be found by first equation of kinematics as

$v=u+at\\\\t=\frac{v-u}{a}\\\\t=\frac{10.28-20}{-9.81}=0.991seconds\approx 1second$

4 0

3 years ago

What did scientists predict the big bang should have left ??

ELEN [110]

<span>radiation, hydrogen, and helium </span>

4 0

3 years ago

Read 2 more answers

Some hypothetical alloy is composed of 12.5 wt% of metal A and 87.5 wt% of metal B. If the densities of metals A and B are 4.27

densk [106]

Answer:

The number of atoms in the unit cell is 2, the crystal structure for the alloy is body centered cubic.

Explanation:

Given that,

Weight of metal A = 12.5%

Weight of metal B = 87.5%

Length of unit cell = 0.395 nm

Density of A = 4.27 g/cm³

Density of B= 6.35 g/cm³

Weight of A = 61.4 g/mol

Weight of B = 125.7 g/mol

We need to calculate the density of the alloy

Using formula of density

$\rho=n\times\dfrac{m}{V_{c}\times N_{A}}$

$n=\dfrac{\rho\timesV_{c}\times N}{m}$ ....(I)

Where, n = number of atoms per unit cells

m = Mass of the alloy

V=Volume of the unit cell

N = Avogadro number

We calculate the density of alloy

$\rho=\dfrac{1}{\dfrac{12.5}{4.27}+\dfrac{87.5}{6.35}}\times100$

$\rho=5.98$

We calculate the mass of the alloy

$m=\dfrac{1}{\dfrac{12.5}{61.4}+\dfrac{87.5}{125.7}}\times100$

$m=111.15$

Put the value into the equation (I)

$n=\dfrac{5.9855\times(0.395\times10^{-9}\times10^{2})^3\times6.023\times10^{23}}{111.15}$

$n=1.99\approx 2\ atoms/cell$

Hence, The number of atoms in the unit cell is 2, the crystal structure for the alloy is body centered cubic.

5 0

4 years ago

What is cocanve mirror?

pochemuha

Answer:

A mirror that has a reflecting surface that is recessed inward is called concave mirror

8 0

3 years ago

Read 2 more answers

Guillaume Amontons first took a stab at measuring absolute zero in 1702. What would be the most reasonable way it would have bee

Oliga [24]

He would measure the speed of molecules as the temperature gets colder until the temperature is measured at which motion stops.

<h3>What is the absolute zero?</h3>

The absolute zero refers to the temperature at which the gas seems to stop moving. Recall that temperature is the measure of the average kinetic energy of the molecules of a gas.

Hence, if Guillaume Amontons first took a stab at measuring absolute zero in 1702, he would measure the speed of molecules as the temperature gets colder until the temperature is measured at which motion stops.

Learn more about absolute zero:brainly.com/question/27951132

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4 0

2 years ago