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3 years ago

An engine does 10 J of work and exhausts 25 J of waste heat during each cycle.

1 answer:

4 0

The thermal efficiency is defined as follows

$\eta = 1 - \frac{Q_{\text{out}}}{Q_\text{in}}$ ,

and the energy which is put into the system is

$Q_{\text{in}} = W_\text{out} + Q_\text{out}$ .

In your case $Q_\text{in} = 25 \text{ J},W_\text{out}=10 \text{ J}.$

So $Q_\text{out}=10 \text{ J}$ which gives an efficiency of

$\eta = 1 - \frac{10 \text{ J}}{25 \text { J}} = 0.6 = 60 \%$ .

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A motorcycle is stopped at a traffic light. When the light turns green, the motorcycle accelerates to a speed of 91 km/h over a

zimovet [89]

Given :

Initial speed , u = 0 m/s .

Final speed , v = 91 km/h = 25.28 m/s .

To Find :

a) Average acceleration .

b ) Assuming the motorcycle maintained a constant acceleration, how far is it from the traffic light after 3.3 s .

Solution :

a )

We know ,by equation of motion :

$v^2-u^2=2as\\\\a=\dfrac{v^2-u^2}{2s}\\\\a=\dfrac{25.28^2-0^2}{2\times 47}\ m/s^2\\\\a=6.8\ m/s^2$

Also , by equation of motion :

$s=ut+\dfrac{at^2}{2}\\\\s=0+\dfrac{6.8\times (3.3)^2}{2}\ m\\\\s=37.02\ m$

Hence , this is the required solution .

6 0

3 years ago

How does an ocean wave transfer energy across the ocean?

Alborosie

The energy travels in a disturbance, in an ocean that disturbance is a wave, so the wave makes energy and moves it through the water

3 0

3 years ago

Two large non-conducting plates of surface area A = 0.25 m 2 carry equal but opposite charges What is the energy density of the

Stells [14]

Answer:

5.1*10^3 J/m^3

Explanation:

Using E = q/A*eo

And

q =75*10^-6 C

A = 0.25

eo = 8.85*10^-12

Energy density = 1/2*eo*(E^2) = 1/2*eo*(q/A*eo)^2 = [q^2] / [2*(A^2)*eo]

= [(75*10^-6)^2] / [2*(0.25)^2*8.85*10^-12]

= 5.1*10^3 J/m^3

8 0

3 years ago

A hollow cylinder of mass 2.00 kg, inner radius 0.100 m, and outer radius 0.200 m is free to rotate without friction around a ho

Aneli [31]

Answer:

h=2.86m

Explanation:

In order to give a quick response to this exercise we will use the equations of conservation of kinetic and potential energy, the equation is given by,

$\Delta PE_i + \Delta KE_i = \Delta PE_f +\Delta KE_f$

There is no kinetic energy in the initial state, nor potential energy in the end,

$mgh+0=0+KE_f$

In the final kinetic energy, the energy contributed by the Inertia must be considered, as well,

$mgh = (\frac{1}{2}mv^2+\frac{1}{2}I\omega^2)$

The inertia of the bodies is given by the equation,

$I=\frac{m(R_1^2+R^2_2)}{2}$

$I=\frac{2(0.2^2+0.1^2)}{2}$

$I=0.05Kgm^2$

On the other hand the angular velocity is given by

$\omega =\frac{v}{R_2}=\frac{4}{1/5} = 2rad/s$

Replacing these values in the equation,

$(0.5)(9.8)(h) =\frac{1}{2}*0.5*4^2+\frac{1}{2}*0.05*20^2$

Solving for h,

$h=2.86m$

5 0

3 years ago

An astronomer is observing a star which puzzles her. The lines in the star's spectrum indicates that the star is very hot and sh

Firlakuza [10]

Answer:

the stars which are red in color are cool.

Explanation:

The stars which has reddish color are cool in nature while those stars which has white and blue in color are very hot in nature. The stars change its color when they becomes hotter , first the star color reddish when they are cool but with increasing temperature it changes the color from reddish to orange then yellow. After yellow it turns green and finally get blue color when the stars are very very hot.

5 0

3 years ago