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Furkat [3]
3 years ago
8

A mechanical device requires 420 J of work to do 230 J of work to lift a crate. What is the efficiency of the device? 190% 0.5%

183% 55%
Physics
2 answers:
erastova [34]3 years ago
8 0

Answer:

55%

Explanation:

Delicious77 [7]3 years ago
4 0

power out / power in so 230/420 = 0.547619048 using sigfiges its about .55 or 55%

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The electric motor of a model train accelerates the train from rest to 0.685 m/s in 21.5 ms. The total mass of the train is 875
Natali [406]

Answer:

P=9.58 W

Explanation:

According to Newton's second law, and assuming friction force as zero:

F_m=m.a\\F_m=0.875kg*a

The acceleration is given by:

a=\frac{\Delta v}{t}\\a=\frac{0.685m/s}{21.5*10^{-3}s}\\\\a=31.9m/s^2

So the force exerted  by the motor is:

F_m=0.875kg*31.9m/s^2\\F_m=27.9N

The work done by the motor is given by:

W_m=F_m*d\\\\d=\frac{1}{2}*a*t^2\\d=\frac{1}{2}*31.9m/s^2*(21.5*10^{-3}s)^2\\\\d=7.37*10^{-3}m

W_m=27.9N*7.37*10^{-3}m\\W_m=0.206J

And finally, the power is given by:

P=\frac{W_m}{t}\\P=\frac{0.206J}{21.5*10^{-3}s}\\\\P=9.58W

8 0
3 years ago
What is the lowest gauge pressure that the average person can achieve inside his lungs? express your answer with the appropriate
eimsori [14]
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hichkok12 [17]

Answer:

891 excess electrons must be present on each sphere

Explanation:

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Using Coulomb's law,

F=[1/4pieo]q1q2/r^2

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