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3 years ago

7

Efficiency of a machine is lesser than 100% , Why?

1 answer:

astra-53 [7]3 years ago

4 0

Answer:

Efficiency is the percent of work put into a machine by the user (input work) that becomes work done by the machine (output work). The output work is always less than the input work because some of the input work is used to overcome friction. Therefore, efficiency is always less than 100 percent.

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Which of the following is NOT a characteristic of scientific knowledge? please help me

kakasveta [241]

I think the correct answer from the choices listed above is the second option. It would be that scientific knowledge can answer all of society's questions that is not a <span>characteristic of scientific knowledge. Hope this answers the question. Have a nice day.</span>

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3 years ago

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Light with a wavelength of 5.0 · 10-7 m strikes a surface that requires 2.0 ev to eject an electron. Calculate the energy, in jo

GenaCL600 [577]

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3 years ago

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The height of a cone is increasing at a rate of 10 cm/sec and its radius is decreasing so that its volume remains constant. How

ki77a [65]

Answer:

dr/dt = -2 cm/s.

Explanation:

The volume of a cone is given by:

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

r is the radius
h is the height

Let's take the derivative with respect to time in each side of (1).

$\frac{dV}{dt}=\frac{1}{3} \pi \frac{d}{dt}(r^{2}h)=\frac{1}{3} \pi \left(2r\frac{dr}{dt}h+r^{2}\frac{dh}{dt} \right)$ (2)

We know that:

dh/dt = 10 cm / s (rate increasing of height)
dV/dt = 0 (constant volume means no variation with respect of time)
r = 4 cm
h = 10 cm

We can calculate how fast is the radius changing using the above information.

$0=\frac{1}{3} \pi \left( 2\cdot 4\cdot \frac{dr}{dt} \cdot 10 + 4^{2}\cdot 10)\right$

Therefore dr/dt will be:

$\frac{dr}{dt}=-\frac{160}{80}=-2 cm/s$

The minus signs means that r is decreasing.

I hope it helps you!

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3 years ago

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you may just select the word answer and then without cutting it u may start to type ur answer then it will be in bold letter

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3 years ago

An object located near the surface of Earth has a weight of a 245 N

marusya05 [52]

Answer:

The mass of the object is 24.5 kg and weight of the object on Mars is 91.14 N.

Explanation:

Weight of the object on the surface of Earth, W = 245 N

On the surface of Earth, acceleration due to gravity, g = 10 m/s²

Weight of an object is given by :

W = mg

m is mass

$m=\dfrac{W}{g}\\\\m=\dfrac{245\ N}{10\ m/s^2}\\\\=24.5\ kg$

So, the mass of the object is 24.5 kg

Acceleration due to gravity on Mars, g' = 3.72 m/s²

Weight of the object on Mars,

W' =mg'

W' = 24.5 kg × 3.72 m/s²

= 91.14 N

So, the weight of the object on Mars is 91.14 N.

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3 years ago