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प्रश्न
The world record for weight lifting was held by Sergei Didyk of the USSR. He lifted 261 kg to a height of 2.3 m in 4s; find:
(a) Weight lifted by him
(b) Work done by him
(c) Power developed by him. (g = 10m/s2)
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उत्तर
(a) Weight lifted by him = m × g = 261 × 10 = 2610 N.
(b) Work done by him = F × d = 261 × 2.3 J = 6003 J.
(c) Power developed by him =`("Work in J")/("Time in s")=6003/4"Watt"` = 1500.75 W.
संबंधित प्रश्न
A boy weighing 40 kgf climbs up a stair of 30 steps each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes. Compare:
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State the condition when the work done by a force is positive. Explain with the help of examples.
A body is moved in a direction opposite to the direction of force acting on it. State whether the work is done by the force or work is done against the force
The work done by a fielder when he takes a catch in a cricket match, is negative. Explain.
State the factors on which moment of force about a point depends.
A man spends 7.4 kJ energy in displacing a body by 74 m in the direction in which he applies force, in 2.5 s. Calculate the power spent (in H.P) by the man.
A man raises a box of mass 50 kg to a height of 2 m in 20s, while another man raises the same box to the same height in 50s. Calculated:
- the work done, and
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What happens to the power if the time for doing work is reduced from t second to t/10 second?
A machine raises a load of 750 N through a height of 16 m in 5 seconds. Calculate the power at which the machine works.
A force of 1 kgf displaces a body by a distance of 10 cm
(i) in direction of force,
(ii) normal to the force
(iii) at an angle of 60° to the direction of the force.
Calculate the amount of work done in each case. (Take: g = 9.8 ms−2 )
