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soldi70 [24.7K]

3 years ago

8

A machine designed to stretch a stiff spring uses 1,550 J of energy to stretch the spring. If the work output is 1,200 J, what i

s the machine’s efficiency?

1 answer:

lapo4ka [179]3 years ago

8 0

Answer:

77%

Explanation:

efficiency= work output/work input X 100%

e = 1,200j/ 1,550 j x100%

e = 1,200/1,550= 0.77

e = 0.77 x 100%

e = 77%

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Let height of twin falls = x
height of seven falls = 2.5x

x + 2.5x = 420
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x = 420/3.5 = 120

so twin falls = x = 120 ft
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3 years ago

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An iron nail is driven into a block of ice by a single blow of a hammer. The hammerhead has a mass of 0.5 kg and an initial spee

larisa [96]

Answer:

The ice melts mass is:

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$K_E = 1/2*m*v^2$

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$K_E=2.56 kg*m^2/s^2$

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Assuming no loss in heat, in the motion so both continue with temperature 0~C

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3 years ago

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evablogger [386]

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3 years ago

You may have noticed runaway truck lanes while driving in the mountains. These gravel-filled lanes are designed to stop trucks t

kati45 [8]

Answer:

The coefficient of kinetic friction $\mu_k = 0.724$

Explanation:

From the question we are told that

The length of the lane is $l = 36.0 \ m$

The speed of the truck is $v = 22.6\ m/s$

Generally from the work-energy theorem we have that

$\Delta KE = N * \mu_k * l$

Here N is the normal force acting on the truck which is mathematically represented as

$\Delta KE$ is the change in kinetic energy which is mathematically represented as

$\Delta KE = \frac{1}{2} * m * v^2$

=> $\Delta KE = 0.5 * m * 22.6^2$

=> $\Delta KE = 255.38m$

$255.38m = m * 9.8 * \mu_k * 36.0$

=> $255.38 = 352.8 * \mu_k$

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3 years ago