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hoa [83]
3 years ago
7

An automobile having a mass of 1100 kg initially moves along a level highway at 120 km/h relative to the highway. It then climbs

a hill whose crest is 80 m above the level highway and parks at a rest area located there. Use a reference with kinetic and potential energy each equal to zero for the stationary highway before the hill. Let g = 9.81 m/s^2.
For the automobile, determine its change in kinetic energy and its change in potential energy, both in kJ. For the automobile, determine its change in kinetic energy, in kJ.
a. -8594
b. -663.1
c. -6.63x10^5
d. 663.1
Engineering
1 answer:
soldier1979 [14.2K]3 years ago
8 0

Answer:

-6111.11\ \text{kJ}

863.28\ \text{kJ}

Explanation:

m = Mass of automobile = 1100 kg

v = Velocity of car = 120 km/h = \dfrac{120}{3.6}\ \text{m/s}

h = Height of hill = 80 m

g = Acceleration due to gravity = 9.81\ \text{m/s}^2

Change in kinetic energy

KE=\dfrac{1}{2}m(u^2-v^2)\\\Rightarrow KE=\dfrac{1}{2}\times 1100\times (0-(\dfrac{120}{3.6})^2)\\\Rightarrow KE=-611111.11\ \text{J}

Change in kinetic energy is -6111.11\ \text{kJ}

Change in potential energy is given by

PE=mgh\\\Rightarrow PE=1100\times 9.81\times 80\\\Rightarrow PE=863280\ \text{J}

The change in potential energy is 863.28\ \text{kJ}.

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100000000000x1000000000000=?
zhannawk [14.2K]

Answer:

Thy answer to your very sophisticated question is 1E23

Explanation:

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The free convection heat transfer coefficient on a thin hot vertical plate suspended in still air can be determined from observa
damaskus [11]

Answer:

h = 6.35 W/m².k

Explanation:

In order to solve this problem, we will use energy balance, taking the thin hot plate as a system. According to energy balance, the rate of heat transfer to surrounding through convection must be equal to the energy stored in the plate:

Rate of Heat Transfer Through Convection = Energy Stored in Plate

- h A (Ts - T₀) = m C dT/dt

where,

h = convection heat transfer coefficient = ?

A = Surface area of plate through which heat transfer takes place = 2 x 0.3 m x 0.3 m (2 is multiplied for two sides of thin plate) = 0.18 m²

Ts = Surface Temperature of hot thin plate = 225⁰C

T₀ = Ambient Temperature = 25°C

m = mass of plate = 3.75 kg

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dT/dt = rate of change in plate temperature = - 0.022 K/s

Therefore,

- h (0.18 m²)(225 - 25) k = (3.75 kg)(2770 J/kg.k)(- 0.022 k/s)

h = (- 228.525 W)/(- 36 m².k)

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4 0
3 years ago
A 55-μF capacitor has energy ω (t) = 10 cos2 377t J and consider a positive v(t). Determine the current through the capacitor.
mart [117]

Given :

Capacitor , C = 55 μF .

Energy is given by :

\omega(t)=10cos^2 (377t)\ J .

To Find :

The current through the capacitor.

Solution :

Energy in capacitor is given by :

\omega=\dfrac{Cv^2}{2}\\\\v=\sqrt{\dfrac{2\omega}{C}}\\\\v=\sqrt{\dfrac{2\times 10cos^2 (377t)}{55\times 10^{-6}}}\\\\v=cos(337t)\sqrt{\dfrac{2\times 10}{55\times 10^{-6}}}\\\\v=603.02\ cos( 337t)

Now , current i is given by :

i=C\dfrac{dv}{dt}\\\\i=C\dfrac{d[603.02cos(337t)]}{dt}\\\\i=-55\times 10^{-6}\times 603.03\times 337\times sin(337t)\\\\i=-11.18\ sin(337t)

( differentiation of cos x is - sin x )

Therefore , the current through the capacitor is -11.18 sin ( 377t).

Hence , this is the required solution .

6 0
3 years ago
Given that the skin depth of graphite at 100 (MHz) is 0.16 (mm), determine (a) the conductivity of graphite, and (b) the distanc
Andrei [34K]

Answer:

the answer is below

Explanation:

a) The conductivity of graphite (σ) is calculated using the formula:

\delta=\frac{1}{\sqrt{\pi f \mu \sigma} }\\\\\sigma =\frac{1}{\pi f \mu \delta^2}

where f = frequency = 100 MHz, δ = skin depth = 0.16 mm = 0.00016 m, μ = 0.0000012

Substituting:

\sigma =\frac{1}{\pi *10^6* 0.0000012*0.00016^2}=0.99*10^4\ S/m

b) f = 1 GHz = 10⁹ Hz.

\alpha=\sqrt{\pi f \mu \sigma} = \sqrt{0.0000012*10^9*\pi*0.99*10^5}=1.98*10^4\ Np/m\\\\20log_{10}  e^{-\alpha z}=-30\ dB\\\\(-\alpha z)log_{10}  e=-1.5 \\\\z=\frac{-1.5}{log_{10}  e*-\alpha} =1.75*10^{-4}\ m=0.175\ mm

4 0
3 years ago
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Answer:

They are both correct

Explanation:

When someone is asking a question of you, it means he or she has either been paying attention, and is interested in you, what you're doing, or what you're saying. Also, silence when used properly can be golden in the sense that it can prevent unnecessary problems from arising, and can save one from a lot of unforeseen problem. Whatever is said cannot be taken back again, and some things should never be said at all, especially in a professional setting.

8 0
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