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3 years ago

8

Day and night are caused by

2 answers:

rjkz [21]3 years ago

7 0

Answer:

the rotation of Earth on its axis

Explanation:

Did it on study island

klemol [59]3 years ago

3 0

Answer:

The Moon rotating around Earth and the Earth rotating around the Sun

Explanation:

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give three examples from the device on the apply page where potential energy was converted to kinetic energy

Elodia [21]

a water turbine drops water onto a blade which gains ke at water's gpe expense

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3 years ago

Example of what happens to particles when their kinetic energy decreases?

Ann [662]

Explanation:

<h2>When we decrease the temperature, less heat energy is supplied to the atoms, and so their average kinetic energy decreases. When they enter a phase transition, such as freezing from a liquid to a solid, the temperature is not decreasing or increasing, and stays constant</h2>

6 0

3 years ago

Read 2 more answers

Identify the two functional groups that react to form polyester.

KiRa [710]

Polyester are commonly made up of an organic alcohol that contains a hydroloxyl and a carboxylic acid which contains a carboxyl. polyester is a class of synthetic polymers built up from multiple chemical repeating units linked together by ester groups. it also displays a wide array of properties and practical applications.

3 0

3 years ago

A river 500 ft wide flows with a speed of 8 ft/s with respect to the earth. A woman swims with a speed of 4 ft/s with respect to

White raven [17]

Answer:

1) $\Delta s=1000\ ft$

2) $\Delta s'=998.11\ ft.s^{-1}$

3) $t\approx125\ s$

$t'\approx463.733\ s$

Explanation:

Given:

width of river, $w=500\ ft$

speed of stream with respect to the ground, $v_s=8\ ft.s^{-1}$

speed of the swimmer with respect to water, $v=4\ ft.s^{-1}$

<u>Now the resultant of the two velocities perpendicular to each other:</u>

$v_r=\sqrt{v^2+v_s^2}$

$v_r=\sqrt{4^2+8^2}$

$v_r=8.9442\ ft.s^{-1}$

<u>Now the angle of the resultant velocity form the vertical:</u>

$\tan\beta=\frac{v_s}{v}$

$\tan\beta=\frac{8}{4}$

$\beta=63.43^{\circ}$

Now the distance swam by the swimmer in this direction be d.

so,

$d.\cos\beta=w$

$d\times \cos\ 63.43=500$

$d=1118.034\ ft$

Now the distance swept downward:

$\Delta s=\sqrt{d^2-w^2}$

$\Delta s=\sqrt{1118.034^2-500^2}$

$\Delta s=1000\ ft$

2)

On swimming 37° upstream:

<u>The velocity component of stream cancelled by the swimmer:</u>

$v'=v.\cos37$

$v'=4\times \cos37$

$v'=3.1945\ ft.s^{-1}$

<u>Now the net effective speed of stream sweeping the swimmer:</u>

$v_n=v_s-v'$

$v_n=8-3.1945$

$v_n=4.8055\ ft.s^{-1}$

<u>The component of swimmer's velocity heading directly towards the opposite bank:</u>

$v'_r=v.\sin37$

$v'_r=4\sin37$

$v'_r=2.4073\ ft.s^{-1}$

<u>Now the angle of the resultant velocity of the swimmer from the normal to the stream</u>:

$\tan\phi=\frac{v_n}{v'_r}$

$\tan\phi=\frac{4.8055}{2.4073}$

$\phi=63.39^{\circ}$

Now let the distance swam in this direction be d'.

$d'\times \cos\phi=w$

$d'=\frac{500}{\cos63.39}$

$d'=1116.344\ ft$

<u>Now the distance swept downstream:</u>

$\Delta s'=\sqrt{d'^2-w^2}$

$\Delta s'=\sqrt{1116.344^2-500^2}$

$\Delta s'=998.11\ ft.s^{-1}$

3)

Time taken in crossing the rive in case 1:

$t=\frac{d}{v_r}$

$t=\frac{1118.034}{8.9442}$

$t\approx125\ s$

Time taken in crossing the rive in case 2:

$t'=\frac{d'}{v'_r}$

$t'=\frac{1116.344}{2.4073}$

$t'\approx463.733\ s$

7 0

4 years ago

A car travels at uniform acceleration over a tine interval of 20.0s. its initial velocity is 11.0m/s and its final velocity is 3

SIZIF [17.4K]

Since the acceleration is uniform, we can calculate it from the data we are given:

a = (vf - vi)/2

where vf=33 m/s and vi=11 m/s

Then use Suvat's equation:

x(t) = vi*t + 0.5 * a * t

where t=20s

3 0

4 years ago