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2 years ago

9. How much energy does a 100 W light bulb use in half an hour? If the light bulb converts

1 answer:

6 0

The energy used by the light bulb in half an hour is 180000 J and the amount of thermal energy generated is 158400 J.

What is Energy?

Energy is the ability or the capacity to do work.

To calculate the energy of the light bulb we use the formula below

Formula:

E = Pt.......... Equation 1

Where:

E = Energy used by the bulb in a half-hour
P = Power of the bulb
t = Time

Given:

P = 100 W
t = 1/2 hour = 30 minutes = (30×60) = 1800 seconds

Substitute these values into equation 1

E = (100×1800)
E = 180000 J

If the light converts 12% of electric energy to light energy, then 88% of the energy is used to generate thermal energy

Therefore,

Thermal energy = (180000×88/100) = 158400 J

Hence, the energy used by the light bulb in half an hour is 180000 J and the amount of thermal energy generated is 158400 J.

Learn more about energy here: brainly.com/question/21927255

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The 4.0 -kg head of an ax is moving at 3 m/s when it strikes a log and penetrates 0.01m into the log. What is the average force

Elina [12.6K]

Answer:

the average force the blade exerts on the log is 1791.05 N.

Explanation:

Given;

mass of the ax head, m = 4 kg

speed of the ax, v = 3 m/s

depth traveled into the log, d = 0.01 m

The time to traveled through the depth;

$s = (\frac{u+v}{2} )t\\\\0.01 = (\frac{0+3}{2} )t\\\\0.01 = 1.5t\\\\t = \frac{0.01}{1.5} \\\\t = 0.0067 \ s$

The average force the blade exerts on the log;

$F = ma=\frac{mv}{t} = \frac{4 \times 3}{0.0067} = 1791.05 \ N \\\\$

Therefore, the average force the blade exerts on the log is 1791.05 N.

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3 years ago

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max2010maxim [7]

Answer:

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3 years ago

All objects emit what radiation

Eduardwww [97]

If an object is not at Absolute Zero, then it is
absorbing and radiating thermal (heat) energy.

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3 years ago

What is the force applied to a baseball that has a mass of 142kg and has a acceleration of 30m/s to the power of 2

aev [14]

Mass=m=142kg
Acceleration=a=30m/s
Force=F

Using Newton's second law

$\\ \sf\Rrightarrow F=ma$

$\\ \sf\Rrightarrow F=142(30)$

$\\ \sf\Rrightarrow F=4260N$

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3 years ago

Where is the near point of an normal eye when accidentally wear a contact lens with a power of +2.0 diopters?

Lerok [7]

Answer:

The near point of an eye with power of +2 dopters, u' = - 50 cm

Given:

Power of a contact lens, P = +2.0 diopters

Solution:

To calculate the near point, we need to find the focal length of the lens which is given by:

Power, P = $\frac{1}{f}$

where

f = focal length

Thus

f = $\frac{1}{P}$

f = $\frac{1}{2}$ = + 0.5 m

The near point of the eye is the point distant such that the image formed at this point can be seen clearly by the eye.

Now, by using lens maker formula:

$\frac{1}{f} = \frac{1}{u} + \frac{1}{u'}$

where

u = object distance = 25 cm = 0.25 m = near point of a normal eye

u' = image distance

Now,

$\frac{1}{u'} = \frac{1}{f} - \frac{1}{u}$

$\frac{1}{u'} = \frac{1}{0.5} - \frac{1}{0.25}$

$\frac{1}{u'} = \frac{1}{f} - \frac{1}{u}$

Solving the above eqn, we get:

u' = - 0.5 m = - 50 cm

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3 years ago