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Elza [17]
3 years ago
15

the useful power out of an electric motor is 20w and the total power into the motor is 80w calculate the percentage efficiency o

f the motor
Physics
1 answer:
olganol [36]3 years ago
4 0

Answer:

25%

Explanation:

Efficiency is the ratio of power out to power in.

e = 20 W / 80 W

e = 0.25

The motor is 25% efficient.

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Calculate the wavelength (in nm) of the blue light emitted by a mercury lamp with a frequency of 6.88 × 1014 Hz. The speed of li
Nezavi [6.7K]

Answer: 430 nm.

Explanation:

The relation of wavelength and frequency is:

Formula used : \nu=\frac{c}{\lambda}

where,

\nu = frequency =6.88\times 10^{14}Hz

\lambda = wavelength  = ?

c = speed of light = 3.00\times 10^{8}m/s

Now put all the given values in this formula, we get

6.88\times 10^{14}=\frac{3.00\times 10^{8}m/s}{\lambda}

\lambda=\frac{3.00\times 10^{8}m/s}{6.88\times 10^{14}}=0.43\times 10^{-6}m=430m        (1nm=10^{-9}m)

Thus the wavelength (in nm) of the blue light emitted by a mercury lamp is 430 nm.

6 0
3 years ago
Suppose I have a spherical insulating shell with inner radius r and outer radius R. The shell has a uniformly distributed charge
a_sh-v [17]

Answer:

3Q / 4 pi (R^3 - r^3)

Explanation:

Charge density = charge / volume

volume of a spherical shell = \frac{4}{3} \pi(R^{3} - r^{3})

4 0
3 years ago
Justin depends 600watts if power pushing a car 10m in 5sec how much force did he exert
Natasha_Volkova [10]

Force exerted by Justin=300 N

Here power= 600 W

distance traveled=10 m

time=5 s

power is given by P= Work done/ time

600=work/5

so work= 60x5=3000J

now work done= force* distance

3000=F *10

F= 3000/10

F=300 N

5 0
3 years ago
The number of electromagnetic waves that travel past a certain point in a given time is the ________ of the radiation.
Rina8888 [55]
The period of the radiation?
8 0
3 years ago
Explain the difference between reversible and irreversible
kirza4 [7]

Answer:

The difference between reversible and irreversible is reversible can be changed but irreversible can not.

7 0
2 years ago
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