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3 years ago

A light bulb has a power output of 80 W and it has been left on for 90 seconds. How much work was done?

1 answer:

3 0

7200 joules of heat and light energy was dissipated into the air. But no work was done ... no force moved through no distance.

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The ceiling of your lecture hall is probably covered with acoustic tile, which has small holes separated by about 5.9 mm. Using

timurjin [86]

Answer:

45.88297 m

Violet

Explanation:

x = Gap between holes = 5.9 mm

$\lambda$ = Wavelength = 527 nm

D = Diameter of eye = 5 mm

L= Distance of observer from holes

From Rayleigh criteria we have the relation

$\frac{x}{L}=1.22\frac{\lambda}{D}\\\Rightarrow L=\frac{xD}{1.22\lambda}\\\Rightarrow L=\frac{5.9\times 10^{-3}\times 5\times 10^{-3}}{1.22\times 527\times 10^{-9}}\\\Rightarrow L=45.88297\ m$

A person could be 45.88297 m from the tile and still resolve the holes

Resolving them better means increasing the distance between the observer and the holes. It can be seen here that the distance is inversely proportional to the wavelength. Violet has a lower wavelength than red so, violet light would resolve the holes better.

5 0

3 years ago

A student standing on a stationary skateboard tosses a textbook with a mass of mb = 1.25 kg to a friend standing in front of him

juin [17]

Answer:

The velocity of the student has after throwing the book is 0.0345 m/s.

Explanation:

Given that,

Mass of book =1.25 kg

Combined mass = 112 kg

Velocity of book = 3.61 m/s

Angle = 31°

We need to calculate the magnitude of the velocity of the student has after throwing the book

Using conservation of momentum along horizontal direction

$m_{b}v_{b}\cos\theta= m_{c}v_{c}$

$v_{s}=\dfrac{m_{b}v_{b}\cos\theta}{m_{c}}$

Put the value into the formula

$v_{c}=\dfrac{1.25\times3.61\times\cos31}{112}$

$v_{c}=0.0345\ m/s$

Hence, The velocity of the student has after throwing the book is 0.0345 m/s.

3 0

3 years ago

If the force on an object is in the negative direction, the work it does on the object must be:.

Inga [223]

Answer:

The work could be either positive or negative, depending on the direction the object moves

Explanation:

6 0

2 years ago

Read 2 more answers

Which of the following has to happen for Earth's shadow to fall on the moon?

Ronch [10]

The correct answer is a, lunar eclipse

6 0

2 years ago

Which statement BEST describes how the body moves?

Alex73 [517]

<h3><u>Answer;</u></h3>

A. Skeletal muscles, which are made of fibers, nerves, and blood vessels, contract in order to make the body move.

<h3><u>Explanation</u>;</h3>

<em><u>Muscular tissues functions in movement and locomotion through its direct connection with the skeletal system. </u></em>
<em><u>Skeletal muscles are responsible for moving the body. The skeletal muscle contractions pull on tendons, which as attached to bones. When the skeletal muscle contraction causes the muscle to shorten, the bone and thus the body par will move. </u></em>
<em><u>Skeletal muscles also provide structural support for the entire body. </u></em>

7 0

3 years ago

Read 2 more answers