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Black_prince [1.1K]

3 years ago

7

NEED HELP FAST PLEASE

1 answer:

Inessa05 [86]3 years ago

6 0

the correct answer is gravity

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How many Oxygen (O) atoms are in the following? H2O + CO2<br><br> 4<br><br> 3<br><br> 2

Contact [7]

There are 3 oxygen atoms

6 0

3 years ago

How does the comet's energy change as it moves from point B to point C?

Oksanka [162]

B. Kinetic energy increase, gravitational potential energy decreases

5 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

Nina [5.8K]

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:

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

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

$t'\approx463.733\ s$

3 0

4 years ago

In order to be _______________ forces, their effects must cancel each other out and not cause a change in the object's motion

Tju [1.3M]

Balancing.

When the same force is applied from both sides,the forces cancel out each other.

4 0

3 years ago

In a waterfall, water falls 60 m. Assume all the potential energy change increases its enthalpy (or internal energy, in this cas

iVinArrow [24]

Answer:

The temperature rise of the water is = 0.14 °c

Explanation:

Height = 60 m

Potential energy change ΔP = $m gh$

ΔP = m × 9.81 × 60

ΔP = (588.6 × m) Joule

Since the Potential energy change is equal to the internal energy change or Enthalpy change.

ΔP = ΔH

Since ΔH = m × C × ΔT

⇒ ΔP = m × C × ΔT

Put all the values in above formula we get

⇒ 588.6 × m = m × 4184 × ΔT

⇒ ΔT= 0.14 °c

Therefore the temperature rise of the water is = 0.14 °c

4 0

3 years ago