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4 years ago

An air bag is used to safely decrease the

1 answer:

7 0

The answer is 1. 4 is incorrect because you can't really decrease the mass of the driver. 3 is incorrect because accelerating the driver would cause more damage than not. 2 is incorrect because decreasing the distance would only cause more damage. 1 is correct because by increasing the length of time the force acts on the driver helps reduce the speed of the driver and cause the drive to sustain less injuries. Hope that helps.

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A heat pump is used to maintain a house at 22°C by extracting heat from the outside air on a day when the outside air temperatur

Ilia_Sergeevich [38]

Answer:

It is enough

Explanation:

To develop the problem it is necessary to take into account the concepts related to the coefficient of performance of a pump.

The two ways in which the performance coefficient can be expressed are given by:

$COP_p = \frac{T_H}{T_H-T_L}$

Where,

$T_H =$ High Temperature

$T_L =$ Low Temperature

And the other way is,

$COP_p = \frac{\dot{Q}}{W}$

Where $\dot{Q}$ is heat rate and W the power consumed.

We have all our terms in Celsius, so we calculate the temperature in Kelvin

$T_H = 22+273 = 295K$

$T_L = 2+273 = 275k$

The rate at which heat is lost is:

$\dot{Q} = 110000kJ/h$

The power consumed by the heat pump is

$\dot{W} = 5kW$

And the coefficient of performance is

$COP_p = \frac{T_H}{T_H-T_L}$

$COP_p = \frac{295}{295-275}$

$COP_p = 14.75$

With this value we can calculate the Power required,

$COP_p = \frac{\dot{Q}}{W}$

$14.75 = \frac{110000}{W}$

$W = \frac{110000}{3600*14.75}$

$W = 2.07kW$

<em>The power consumed is consumed is 5kW which is more than 2.07kW so this heat pump powerful enough.</em>

4 0

3 years ago

it takes 840s to walk completely around a circular track, moving at a speed of 1.20m/s? what is the radius of the track?

Tcecarenko [31]

Answer:

160.43 meters

Explanation:

T=(2*pi*r)/v

840=(2*pi*r)/1.2

1008=2*pi*r

504=pi*r

160.43=radius

6 0

3 years ago

For each telecommunications bonding conductor there shall be a label and it shall be located on the conductor as close as practi

shepuryov [24]

Answer:

There shall be a LABEL

Explanation:

The label is to enable the maintenance personal or the user to identify the individual conductor from each other during removal and installation or when maintenance task is being carried out on the system. This is to avoid the users of the system form plugging the conductor incorrectly.

For example, if there are four conductors label A, B, C, and D there will be four connection point label same way. By this, the user will not plug conductor A to plug B.

3 0

4 years ago

Why sound heard better at night than at day?

vodomira [7]

Answer:

it is because it is quieter at night than in the daytime. Therefore it is easy to hear the sound far away. However, it is only one of the reasons. Actually, sound transmits farther at night may be related to refraction of sound waves! First, sound is the vibration of air, and it is a kind of wave motion.

Explanation:

6 0

4 years ago

Read 2 more answers

You drop a batitin a stationary elevator and the ball hits the floor in o 50 s. How long does it take for the ball to hit the fl

solmaris [256]

Answer:

option (a) 0.61 s

Explanation:

Given;

Time taken by the ball to reach the ground = 0.50 s

Let us first calculate the distance through which the ball falls on the ground

from the Newton's equation of motion, we have

$s=ut+\frac{1}{2}at^2$

where,

s is the distance

a is the acceleration

t is the time

here it is the case of free fall

thus, a = g = acceleration due to gravity

u = initial speed of the ball = 0

on substituting the values, we get

$s=0\times 0.50+\frac{1}{2}\times9.8\times0.50^2$

s = 1.225 m

Now,

when the elevator is moving up with speed of 1.0 m/s

the initial speed of the ball = -1.0 m/s (as the elevator is moving in upward direction)

thus , we have

$s=ut+\frac{1}{2}at^2$

$1.225=-1.0\times\ t+\frac{1}{2}\times9.8t^2$

4.9t^2 - t - 1.225 = 0

t = 0.612 s

hence, the correct answer is option (a) 0.61 s

4 0

4 years ago