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satela [25.4K]
3 years ago
9

Karen has a mass of 57.9 kg as she rides the up escalator at Woodley Park Station of the Washington D.C. Metro. Karen rode a dis

tance of 69.6 m, the longest escalator in the free world. The acceleration of gravity is 9.8 m/s 2 . How much work did the escalator do on Karen if it has an inclination of 34.8 ◦ ? Answer in units of J.
Physics
2 answers:
liq [111]3 years ago
8 0

Answer:22537.92 J

Explanation:

Given

mass of karen \left ( m\right )=57.9 kg

Distance covered by Karen =69.6 m

acceleration due to gravity=9.8

inclination=34.8^{\circ}

vertically karen move

h=69.6\times \sin \left ( 34.8\right )

h=39.72 m

Work done by escalator on karen is equal to change in potential energy of  karen

\Delta P.E.=m\times g\times \Delta h

\Delta P.E.=57.9\times 9.8\times 39.72=22537.92 J

Oxana [17]3 years ago
4 0

Answer:

22537.92 J

Explanation:

We are given that

Mass of Karen=57.9 Kg

Karen rode  a distance=69.6 m

Acceleration due to gravity=9.8 m/s^2

\theta=34.8^{\circ}

We have to find the amount of work done by escalator on Karen.

Vertical height of longest escalator=69.6 sin 34.8^{\circ}=39.72 m

Work done=Potential energy of escalator

Work done=mgh=57.9\times 9.8\times 39.72=22537.92 J

Hence, the work done on Karen=22537.92 J

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The position of a car at time t is given by the function p(t)=t2 2t−4. What is the velocity when p(t)=11? assume t≥0
AysviL [449]

The velocity when function p(t)=11 is 8 .

According to the question

The position of a car at time t  represented by function :

p(t)=t^{2} +2t-4

Now,

When  function p(t) = 11 , t will be

p(t)=t^{2} +2t-4

11 = t²+2t-4

0 = t² + 2t - 15

or

t² +2t-15 = 0

t² +(5-3)t-15 = 0

t² +5t-3t-15 = 0

t(t+5)-3(t+5) = 0

(t-3)(t+5) = 0  

t = 3 , -5  

as t cannot be -ve as given ( t≥0)

so,

t = 3

Now,

the velocity when p(t)=11

As we know velocity = \frac{position}{time}

therefore to get the value of velocity from  function p(t)

we have to differentiate the function with respect to time

\frac{d(p(t))}{dt} =\frac{d}{dt} (t^{2} +2t-4)

v(t) = 2t + 2  

where v(t) = velocity at that time

as t = 3 for  p(t)=11  

so ,

v(t) = 2t + 2  

v(t) = 2*3 + 2  

v(t) = 8

Hence, the velocity when function p(t)=11 is 8 .

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brainly.com/question/12431044

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4 0
2 years ago
Calculate the volume of this regular solid.
Nataly [62]

Answer:

V = 42.41cm^3

Explanation:

In order to calculate the volume of the solid, you use the following formula:

V=\frac{1}{3}\pi r^2 h

where

r: radius of the circular base of the cone = 3 cm

h: height from the circular base to the peak of the cone = 4.5 cm

You replace the values of r and h in the formula for the volume V:

V=\frac{1}{3}\pi(3cm)^2(4.5)=42.411cm^3\approx42.41cm^3

hence, the volume of the solid is 42.41 cm^3

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3 years ago
If a 1,000-kg car is traveling at 20.0 m/s when it reaches the bottom of a circular hill of radius 8.00 m, what normal force doe
scoray [572]

Answer:

i don't know this one.

Explanation:

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3 years ago
A cave rescue team lifts an injured spelunker directly upward and out of a sinkhole by means of a motor-driven cable. The lift i
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Answer:

Total work done = = 29811.60 J

Explanation:

Since the person is being moved upward, the person’s potential and kinetic energy are increasing.

To determine the increase in potential energy, the following equation is used;

∆ PE = m * g * ∆ h

m = 78.0 Kg, g = 9.8 m/s, ∆ h = 13.0 m

∆ PE = 78.0 * 9.8 * 13.0 = 9937.20 J

Increase in kinetic energy is given by the following equation;

∆ KE = ½ * m * (vf² – vi²)

vf = 3.4, vi = 0

∆ KE = ½ * 78.0 * 3.4² = 450.84 J

Total work = 9937.20 + 450.84 = 10388.04 J

(b) He is then lifted at the constant speed of 3.40 m/s

Velocity is constant, therefore, there is no increase in kinetic energy. The only work done is the increase of potential energy

∆ PE = 78.0 * 9.8 * 13.0

∆ PE = 9937.20 J

(c) He is then decelerated to zero speed.

Since his velocity decreased from 3.40 m/s to 0 m/s, his kinetic energy decreased.

∆ KE = ½ * 78.0 * (0² - 3.4²)

∆ KE = - 450.84 J

∆ PE = 78.0 * 9.8 * 13.0 = 9937.20 J

Total work = 9937.20 - 450.84 = 9486.36 J

Sum of works = 10388.04 + 9937.20 + 9486.36 = 29811.60 J

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3 years ago
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They point towards a negative charge.
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