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MaRussiya [10]
3 years ago
6

A man holds a child on his shoulders while watching a football match. How many work has he done if the game lasts for 2 hours? ​

Physics
2 answers:
Sedaia [141]3 years ago
8 0
Answer: ZERO!

work= F•d = F*d*cos(theta)

Since there is no displacement taking place then there is NO WORK being done! Cheers!
Shalnov [3]3 years ago
4 0

very interesting and amazing question u had asked but i get it...

Answer

  • work done is given by

W = Force × Displacement

  • but in above case force is exerted on the men as the weight of the child × gravitational pull of earth (9.8 m/s^2) but the displacement or movement is ZERO
  • there for W= F×0 =0
  • so even after carrying child for 2 hours work done by the men will be zero

<u>More</u><u> </u><u>examples</u>

  • a person standing straight and lifting weight
  • a person carry some weight and walk in a circular path and came back to its original position.........in this case also Displacement will be zero

------------------------------------

hope it helped u buddy

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Answer:

Final velocity = 119.83 m/s

Final elevation = 731.9 m

Explanation:

We are told that temperature of air changes from 0 to 10°C

Thus;

Change in temperature; ΔT = 10 - 0 = 10°C

Also, its velocity changes from zero to a final velocity. Thus;

v1 = 0 m/s

v2 is unknown

Also, its elevation changes from zero to a final elevation.

So, z1 = 0 and z2 is unknown

Now, we want to find v2 and z2 when the internal, kinetic and potential energy are equal.

Thus Equating the formula for both kinetic and internal energy gives;

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m will cancel out and v1 is zero to give;

v2² = 2c_v•ΔT

v2 = √(2c_v•ΔT)

Where c_v is specific heat of constant volume of air with a constant value of 718 J/Kg.K

Thus;

v2 = √(2 × 718 × 10)

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To find z2, we will equate potential energy formula to that of the internal energy.

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mg(z2 - z1) = mc_v•ΔT

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z2 = (c_v•ΔT)/g

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4 0
3 years ago
A vertical spring stretches 9.6 cm when a 1.3 kg block is hung from its end. (a) Calculate the spring constant. This block is th
tatiyna

Answer:

F = - K x

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