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3 years ago

Pick the best description of energy efficiency?

1 answer:

8 0

The answer is B. Efficiency is equal to the ratio of energy you get out (output) to the energy you put in (input). Say for a basic example you got a converted output of 40W from 50W input, you'll have an efficiency of 80 percent only.

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Help, I’m stuck. Will give Brainly + 22 pts up for grabs !

Nana76 [90]

Answer:

let the speed of Allegra be x mph, then speed of Elliana is x+4 mph,

time to cover distance for Eliana is 2 hours, time to cover distance for Allegrais 2.5 hours,

since they both cover the same distance you have this,

distance (of Eliana) = distance (of Allegrais ),

distance=speed x time, so we have

speed (of Eliana) x time (of Eliana) = speed (of Allegra) x time (of Allegra),

2(x+4)=2.5x,

solve for x, then substitute back for speeds for Eliana and Allegra,

Eliana's speed = 16 + 4 = 20.

Allegra's speed = 16

6 0

3 years ago

8. An unpowered flywheel is slowed by a constant frictional torque. At time t = 0 it has an angular velocity of 200 rad/s. Ten s

allsm [11]

Answer:

a) $\omega = 50\,\frac{rad}{s}$ , b) $\omega = 0\,\frac{rad}{s}$

Explanation:

The magnitude of torque is a form of moment, that is, a product of force and lever arm (distance), and force is the product of mass and acceleration for rotating systems with constant mass. That is:

$\tau = F \cdot r$

$\tau = m\cdot a \cdot r$

$\tau = m \cdot \alpha \cdot r^{2}$

Where $\alpha$ is the angular acceleration, which is constant as torque is constant. Angular deceleration experimented by the unpowered flywheel is:

$\alpha = \frac{170\,\frac{rad}{s} - 200\,\frac{rad}{s} }{10\,s}$

$\alpha = -3\,\frac{rad}{s^{2}}$

Now, angular velocities of the unpowered flywheel at 50 seconds and 100 seconds are, respectively:

a) t = 50 s.

$\omega = 200\,\frac{rad}{s} - \left(3\,\frac{rad}{s^{2}} \right) \cdot (50\,s)$

$\omega = 50\,\frac{rad}{s}$

b) t = 100 s.

Given that friction is of reactive nature. Frictional torque works on the unpowered flywheel until angular velocity is reduced to zero, whose instant is:

$t = \frac{0\,\frac{rad}{s}-200\,\frac{rad}{s} }{\left(-3\,\frac{rad}{s^{2}} \right)}$

$t = 66.667\,s$

Since $t > 66.667\,s$ , then the angular velocity is equal to zero. Therefore:

$\omega = 0\,\frac{rad}{s}$

7 0

4 years ago

Distance between gas molecules in the case of:

alexira [117]

Answer:

-Increase in temperature: increase

-Decrease in temperature: decrease

-Increase in volume: increase

-Decrease in volume: decrease

-Increase in pressure: increase

-Decrease in pressure: decrease

Explanation:

-Increase in temperature:

● Molecules gain kinetic energy and move fast thus increasing distance

-Decrease in temperature:

● Kinetic energy of molecules decrease so they have smaller distance

-Increase in volume:

● Molecules have more space to move around so distance increase

-Decrease in volume:

● Less space, molecules collide with each other because of decreased distance thus increasing pressure

-Increase in pressure

● Molecules collide with each other and the walls of container increasing pressure so molecules move faster and it increases distance

-Decrease in pressure:

● Molecules collide with each other and walls of container less frequently so distance between molecules decrease

7 0

3 years ago

A block of mass 4 kilograms is initially moving at 5m/s on a horizontal surface. There is friction between the block and the sur

Dmitriy789 [7]

Answer:

d = 2.54 [m]

Explanation:

Through the theorem of work and energy conservation, we can find the work that is done. Considering that the energy in the initial state is only kinetic energy, while the energy in the final state is also kinetic, however, this is zero since the body stops.

$E_{k1}+W=E_{k2}\\$