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Thepotemich [5.8K]

3 years ago

9

Dolphins and other sea creatures can leap to great heights by swimming straight up and exiting the water at a high speed. A 200

kg dolphin leaps straight up to a height of 7.8 m . When the dolphin reenters the water, drag from the water brings it to a stop in 1.8 m . Assuming that the force of the water on the dolphin stays constant as it slows down.
a. How much time does it take for the dolphin to come to rest?
b. What is the force of the water on the dolphin as it is coming to rest?

1 answer:

scoundrel [369]3 years ago

5 0

Answer:

i don't know sorry

Explanation:

so if a pie is baked

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A composite load consists of three loads connected in parallel. One draws 100 W at a PF of 0.92 lagging, another takes 250 W at

fenix001 [56]

Answer:

a) $I_{RMS} = 4.79 A$

b) $PF = 0.908$

Explanation:

Get the reactive powers for each of the loads:

Reactive power = Real Power * tanθ

For load 1

Active power, P₁ = 100 W

Power factor, $cos \theta_{1} = 0.92$

$\theta_{1} = cos^{-1} 0.92\\\theta_{1} = 23.074$

$Q_{1}= P_{1} tan \theta_{1} \\Q_{1}= 100tan 23.074\\Q_{1}= 42.60 W$

For load 2

Active power, P₂ = 250 W

Power factor, $cos \theta_{2} = 0.8$

$\theta_{2} = cos^{-1} 0.8\\\theta_{2} = 36.87$

$Q_{2}= P_{1} tan \theta_{2} \\Q_{2}= 250tan 36.87\\Q_{2}= 187.5 W$

For load 3

Active power, P₃ = 250 W

Power factor, $cos \theta_{3} = 1$

$\theta_{3} = cos^{-1} 1\\\theta_{3} =0$

$Q_{2}= P_{1} tan \theta_{3} \\Q_{3}= 150tan 0\\Q_{3}= 0 W$

Calculate the total reactive power, $Q_{net} = 42.6 + 187.5 + 0$

$Q_{net} = 230.1 W$

Calculate the total active power, $P_{net} = 100 + 250 + 150 = 500 W$

$S_{net} = P_{net} + Q_{net} \\S_{net} = 500 + j230.1$

$P_{net} = IVcos \theta_{net}$

$\theta_{net} = tan^{-1} \frac{230.1}{500} \\\theta_{net} = 24.712$

V = 115 $V_{rms}$

$500 = I_{RMS} * 115 cos 24.712\\I_{RMS} = 500/104.47\\ I_{RMS} = 4.79 A$

b) Power factor of the composite load is $cos\theta_{net}$

$\theta_{net} = 24.712\\PF = cos 24.712\\PF = 0.908$

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3 years ago

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CaHeK987 [17]

Answer:

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Explanation:

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6 0

3 years ago

The potential energy for a mass on a spring is proportional to the square of which of these quantities? A. mass B. frequency C.

frutty [35]

<h2>Answer:Displacement</h2>

Explanation:

Potential energy is present in a spring because the spring is elongated and some work is done it to elongate it.

The elastic potential energy present in a spring is given by $kx^{2}$

where $k$ is the spring constant.It may vary from spring to spring and $x$ is the displacement of the spring from its equalibrium position.

It is evident from the equation that potential energy in the spring increases as $x^{2}$ increases.

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A train is accelerating at a rate of 2 km/hr/s. If its initial velocity is 20 km/hr, what is its velocity after 30 seconds?

Aleksandr [31]

"2 km/hr/s" means that in each second, its engines can increase its speed by 2 km/hr.

If it keeps doing that for 30 seconds, its speed has increased by 60 km/hr.

On top of the initial speed of 20 km/hr, that's 80 km/hr at the end of the 30 seconds.

This whole discussion is of <em>speed</em>, not velocity. Surely, in high school physics,
you've learned the difference by now. There's no information in the question that
says anything about the train's <em>direction</em>, and it was wrong to mention velocity in
the question. This whole thing could have been taking place on a curved section
of track. If that were the case, it would have taken a team of ace engineers, cranking
their Curtas, to describe what was happening to the velocity. Better to just stick with
speed.

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Jet001 [13]

Answer:

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