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3 years ago

The efficiency of a machine is always less than 100% because part of the energy input is used to

Physics

1 answer:

Travka [436]3 years ago

5 0

Answer:

C. Overcome Friction

Explanation:

When using any machine usually those with moving parts, you may notice heat forming near the areas where most movement occurs. As friction continues, more energy is used up and released as heat. For that reason, the efficiency of a machine will forever be less than 100%

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A 100-kg spacecraft is in a circular orbit about Earth at a height h = 2RE .

maria [59]

To solve this problem it is necessary to apply the concepts related to the conservation of the Gravitational Force and the centripetal force by equilibrium,

$F_g = F_c$

$\frac{GmM}{r^2} = \frac{mv^2}{r}$

Where,

m = Mass of spacecraft

M = Mass of Earth

r = Radius (Orbit)

G = Gravitational Universal Music

v = Velocity

Re-arrange to find the velocity

$\frac{GM}{r^2} = \frac{v^2}{r}$

$\frac{GM}{r} = v^2$

$v = \sqrt{\frac{GM}{r}}$

PART A ) The radius of the spacecraft's orbit is 2 times the radius of the earth, that is, considering the center of the earth, the spacecraft is 3 times at that distance. Replacing then,

$v = \sqrt{\frac{(6.67*10^{-11})(5.97*10^{24})}{3*(6.371*10^6)}}$

$v = 4564.42m/s$

From the speed it is possible to use find the formula, so

$T = \frac{2\pi r}{v}$

$T = \frac{2\pi (6.371*10^6)}{4564.42}$

$T = 8770.05s\approx 146min\approx 2.4hour$

Therefore the orbital period of the spacecraft is 2 hours and 24 minutes.

PART B) To find the kinetic energy we simply apply the definition of kinetic energy on the ship, which is

$KE = \frac{1}{2} mv^2$

$KE = \frac{1}{2} (100)(4564.42)^2$

$KE = 1.0416*10^9J$

Therefore the kinetic energy of the Spacecraft is 1.04 Gigajules.

8 0

2 years ago

There is a refrigerator running in a room, the heat flowing into the refrigerator from the outside is 40 J/s, and the refrigerat

Mamont248 [21]

Answer:

(A) 140 j/sec (b) 1.26 K

Explanation:

We have given the heat heat flowing into the refrigerator = 40 J/sec

Work done = 40 W

(a) So the heat discharged from the refrigerator $=heat\ flowing\ in\ refrigerator+work\ done=40+100=140j/sec$

(b) Total heat absorbed =140 j/sec $=140\times 3600=504000j/hour$

Let the temperature be $\Delta T$

Heat absorbed per hour =504000 $[tex]=400\times 10^3\times \Delta T$

So $\Delta T=\frac{504000}{400000}=1.26K$

8 0

3 years ago

A 300 kg car initially travels with a velocity of 20 m/s to the right. A net force F acts on the car for 5 s, which causes the v

hram777 [196]

Answer:

600N.

Explanation:

From the question, we are to calculate the net force acting on the car.

According to Newton's second law of motion:

F = ma

m is the mass of the car

a is the acceleration = change in velocity/Time

a = v-u/t

F = m(v-u)/t

v is the final velocity = 30m/s

u is the initial velocity = 20m/s

t is the time = 5secs

m = 300kg

Get the net force:

Recall that: F = m(v-u)/t

F = 300(30-20)/5

F = 60(30-20)

F = 60(10)

F = 600N

Hence the net force acting on the car is 600N.

3 0

3 years ago

If the mass of a material is 87 grams and the volume of the material is 14 cm3, what would the density of the material be?

tresset_1 [31]

Answer:

6.214g/cm³

Explanation:

The question is on density of a material

Density=mass/volume

Given, mass=87grams and volume= 14 cm³ density=?

Density=m/v 87/14 =6.214g/cm³

8 0

3 years ago

For each of the following, describe the relationship as directly or inversely proportional:

Maksim231197 [3]

The relationships can best be described as follows:
As frequency increases, wavelength decreases. The greater the energy, the larger the frequency and the shorter (smaller) the wavelength. 

a) wavelength vs. frequency = inversely proportional
b) wavelength vs. energy = inversely proportional
c) frequency vs. energy = directly proportional

Hope this answers the questions. Have a nice day. Feel free to ask more questions.

7 0

3 years ago