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4 years ago

When scientists state that energy transformation are inefficient, do they mean energy is destroyed? Explain why.

Physics

1 answer:

TiliK225 [7]4 years ago

6 0

no. energy is not created or destroyed, just transformed.

a hot light source is less efficient than a cold one ... heat is not light ...

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A sound wave traveling at STP has a period of .0023 seconds. The wavelength of this sound is closest to

agasfer [191]

Answer: 3

Wavelength = 0.76m

Explanation:

When sound wave is travelling at standard temperature and pressure ( STP), its speed will be equal to normal speed of sound which is equal to 331 m/s

Given that the period of the wave is 0.0023 seconds.

Wave speed = wavelength/period

Substitute the wave speed and the period to obtain wavelength

331 = wavelength/0.0023

Cross multiply

Wavelength = 331 × 0.0023

Wavelength = 0.7613 metre

The wavelength of this sound is closest to 0.76 m

4 0

4 years ago

A small mailbag is released from a helicopter that is descending steadily at 3 m/s.

mario62 [17]

<u>Answer:</u>

a) Speed of mailbag after 3 seconds = 32.4 m/s

b) Package is 44.1 meter below helicopter

c) If the helicopter was rising steadily at 3.00 m/s

Speed of mailbag after 3 seconds = 26.4 m/s

Package is 44.1 meter below helicopter

<u>Explanation:</u>

a) We have equation of motion, v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration and t is the time taken.

Initial velocity = 3 m/s, acceleration = 9.8 $m/s^2$ and time = 3 seconds.

v = 3+9.8*3 = 32.4 m/s

Speed of mailbag after 3 seconds = 32.4 m/s

b) We have equation of motion , $s= ut+\frac{1}{2} at^2$ , s is the displacement, u is the initial velocity, a is the acceleration and t is the time.

Velocity of helicopter = 3 m/s, time taken = 3 seconds, acceleration = 0 $m/s^2$ .

$s= 3*3+\frac{1}{2} *0*3^2\\ \\ s=9m$

Distance traveled by helicopter = 9 meter.

Velocity of package = 3 m/s, time taken = 3 seconds, acceleration = 9.8 $m/s^2$ .

$s= 3*3+\frac{1}{2} *9.8*3^2\\ \\ s= 53.1m$

Distance traveled by package = 53.1 meter.

So package is (53.1-9)meter below helicopter = 44.1 m

c) Initial velocity = -3 m/s, acceleration = 9.8 $m/s^2$ and time = 3 seconds.

v = -3+9.8*3 = 26.4 m/s

Speed of mailbag after 3 seconds = 26.4 m/s

Velocity of helicopter = -3 m/s, time taken = 3 seconds, acceleration = 0 $m/s^2$ .

$s= -3*3+\frac{1}{2} *0*3^2\\ \\ s=-9m$

Distance traveled by helicopter = 9 meter.

Velocity of package = -3 m/s, time taken = 3 seconds, acceleration = 9.8 $m/s^2$ .

$s= -3*3+\frac{1}{2} *9.8*3^2\\ \\ s= 35.1m$

Distance traveled by package = 35.1 meter.

So package is (35.1+9)meter below helicopter = 44.1 m

4 0

4 years ago

a string of fifty 15 ohm christmas tree lights are connected in series. one burns out, they all burn out. calculate the total re

sesenic [268]

Answer:

The total resistance is 750 [ohm]

Explanation:

To solve this problem we must remember that when we have resistors connected in series, these are added each by the resistance value, in this way we have:

Rt = 15 * 50 = 750 [ohm]

4 0

3 years ago

A 1210-kg vehicle is moving along a horizontal surface with a speed of 28.3 m/s. What work (in J) must be done by the brakes to

ArbitrLikvidat [17]

Answer:

4.85*10^5 Joules

Explanation:

The work done in bringing the car to rest would be equivalent to the kinetic energy of the vehicle while it is in motion.

The kinetic energy of the vehicle is 1/2mv^2; where m is the mass and v is the velocity.

Work done=1/2*1210*28.3^2

Another approach would be to calculate the force applied and the braking distance of the vehicle and then applying the formula of work done. However, it would've been an unnecessary hassle.

6 0

3 years ago

On a recent adventure trip, Anita Break went rock-climbing. Anita was able to steadily lift her 800- kg body 20.0 meters in 100

Irina-Kira [14]

Answer:

Anita 's power rating during this portion of the climb is 1568 Watts.

Explanation:

Given that,

Mass of the body, m = 800 kg

Height, h = 20 m

Time, t = 100 s

We need to find the Anita 's power rating during this portion of the climb. Power rating of an object is given by the work done per unit time. It is given by :

$P=\dfrac{W}{t}$

$P=\dfrac{mgh}{t}$

$P=\dfrac{800\times 9.8\times 20}{100}$

P = 1568 Watts

So, Anita 's power rating during this portion of the climb is 1568 Watts. Hence, this is the required solution.

6 0

3 years ago