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natta225 [31]
3 years ago
5

engineers who design battery operated devices suck as sell phones and MP3 players try to make them as efficient as possible. An

engineer test a cell phone and finds that the batteries supply 10,000 J of energy to make 5,500 J of output energy in the form of sound and light for the screen. How efficient is the phone
Physics
1 answer:
ICE Princess25 [194]3 years ago
8 0
If the 5,500 J of sound and light is the ONLY useful output
from the phone, then the phone's efficiency is

                   (5,500J / 10,000J)  =  0.55  =  55% .

But the test engineer forgot one little minor almost insignificant detail.
As a test engineer myself, I'd say that he needs to turn in his laptop
and soldering iron, and think about changing his career to a job for
which he may be better suited, like 8 hours a day in a highway toll-booth.  

What about that little radio transmitter and receiver inside the phone,
that maintain digital RF communication with the nearest cell tower ?
Without that microscopic radio transceiver ... plus 30 or 40 apps
that are always running unless you shut them off ... the device in your
pocket is essentially a flat rock with one side that sometimes glows.
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Rocket-powered sleds are been used to test the responses of humans to acceleration. Starting from rest, one sled can reach a spe
Greeley [361]

Answer:cho  v₀ =0s  

α=Δv/Δt

Explanation:

\frac{0-495}{2,16-1,78}

=-1302,631579

chuyển động chậm dầnđều

3 0
2 years ago
When energy is produced in a reaction it
goblinko [34]
The correct answer is b i believe
4 0
3 years ago
A bullet with a mass m b = 11.5 g is fired into a block of wood at velocity v b = 249 m/s. The block is attached to a spring tha
Ostrovityanka [42]

Answer:

0.358Kg

Explanation:

The potential energy in the spring at full compression = the initial kinetic energy of the bullet/block system

0.5Ke^2 = 0.5Mv^2

0.5(205)(0.35)^2 = 12.56 J = 0.5(M + 0.0115)v^2

Using conservation of momentum between the bullet and the block

0.0115(265) = (M + 0.0115)v

3.0475 = (M + 0.0115)v

v = 3.0475/(M + 0.0115)

plugging into Energy equation

12.56 = 0.5(M + 0.0115)(3.0475)^2/(M + 0.0115)^2

12.56 = 0.5 × 3.0475^2 / ( M + 0.0115 )

12.56 = 0.5 × 9.2872/ M + 0.0115

12.56 = 4.6436/ M + 0.0115

12.56 ( M + 0.0115 ) = 4.6436

12.56M + 0.1444 = 4.6436

12.56M = 4.6436 - 0.1444

12.56 M = 4.4992

M = 4.4992÷12.56

M = 0.358 Kg

4 0
3 years ago
You are directed to set up an experiment in which you drop, from shoulder height, objects with similar surface areas but differe
tangare [24]

Answer: c. they will hit the ground at the same time

Explanation:

The volume of both objects is almost the same, so the force of friction will be the same in each one, so we can discard it.

Now, when yo drop an object, the acceleration of the object is always g = 9.8m/s^2 downwards, independent of the mass of the object.

So if you drop two objects with the same volume but different mass, because the acceleration is the same for both of them, they will hit the ground at the same time, this means that the density of the object has no impact in how much time the object needs to reach the floor.

So the correct option is c

3 0
3 years ago
Consider f(x) = -4x2 + 24x + 3. Determine whether the function has a maximum or minimum value. Then find the
murzikaleks [220]

Answer:

The function has a maximum in x=3

The maximum is:

f(3) = 39

Explanation:

Find the first derivative of the function for the inflection point, then equal to zero and solve for x

f(x)' = -4*2x + 24=0

-4*2x + 24=0

8x=24

x=3

Now find the second derivative of the function and evaluate at x = 3.

If f (3) ''< 0 the function has a maximum

If f (3) '' >0 the function has a minimum

f(x)''= 8

Note that:

f(3)''= -8

the function has a maximum in x=3

The maximum is:

f(3)=-4(3)^2+24(3) + 3\\\\f(3) = 39

4 0
3 years ago
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