Question

How many Joules of energy does a 100-watt light bulb use per hour? How fast would a 70 kg person have to run to have that amount of kinetic energy

Answer 1

Answer:

1ꜱᴛ ᴀɴꜱᴡᴇʀ

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ꜰʀᴏᴍ ᴛʜᴇ ʀᴇʟᴀᴛɪᴏɴ ʙᴇᴛᴡᴇᴇɴ ᴇɴᴇʀɢʏ ᴀɴᴅᴅ ᴘᴏᴡᴇʀ , ᴘ = ᴡ /△t ,

ꜰɪɴᴅ ᴡ , ᴛʜᴇ ᴇɴᴇʀɢʏ ᴛʜᴇᴇ ʙᴜʟʙ ᴜꜱᴇꜱ .

ᴛʜᴇɴ , ᴡ = ᴋ = 1/2 м υ 2

ᴡ = ᴘ t = (100ᴡ) (3600ꜱ) = 3.6 × 10 '5 ᴊ

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2ɴᴅ ᴀɴꜱᴡᴇʀ

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ᴋ =3.6 × 10 '5 ᴊ

υ = \/ 2ᴋ / m = 2 ( 3. 6 × 10 '5 ᴊ ) / 70 ᴋg

= 100 m/s

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֎࿅ hemaboro࿅֍

Answer 2

Given: A 100-watt light bulb used for an hour. A 70 kg person has to run to have that amount of kinetic energy.

To find: Joules of energy the light bulb uses. Speed of the 70kg person.

Solution:

• The formula of power is given by,

        $P = \frac{E}{t}$

• Here, P is the power of the light bulb, E is the energy consumed by it and t is the time period.
• Here, the time period is given as 1 hour and when converted to its S.I. unit it is equal to 3600 seconds.
• On replacing the terms with the values given in the question,

        $100 W = \frac{E}{3600s}$

        $E = 3.6 * 10^{5} J$

• The formula of kinetic energy is given by,

        $E = \frac{1}{2} mv^{2}$

• Here, E is the kinetic energy, m is the mass and v is the speed or the velocity of the person.
• On replacing the terms with the values given in the question,

        $3.6 * 10^{5} J = \frac{1}{2} (70kg)v^{2}$

        $v = 10285.71 ms^{-1}$

Therefore, 3.6×10⁵ J of energy is used by the light bulb and the speed of the 70 kg person is 10285.71 ms⁻¹.