A spherical ball of mass 20 kg is stationary at the top of a hill of height 100 m. It rolls down a smooth surface to the ground, then climbs up another hill of height 30 m and finally rolls down to a horizontal base at a height of 20 m above the ground. The velocity attained by the ball is from Physics Work, Energy and Power Class 11 Manipur Board
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A spherical ball of mass 20 kg is stationary at the top of a hill of height 100 m. It rolls down a smooth surface to the ground, then climbs up another hill of height 30 m and finally rolls down to a horizontal base at a height of 20 m above the ground. The velocity attained by the ball is

  • 40 m/s

  • 20 m/s

  • 10 m/s

  • 10 square root of 30 m/s


A.

40 m/s

mgh space equals space 1 half mv squared
straight v equals space square root of 2 gh end root
space equals square root of 2 space straight x space 10 space straight x 80 end root space equals 40 space straight m divided by straight s
mgh space equals space 1 half mv squared
straight v equals space square root of 2 gh end root
space equals square root of 2 space straight x space 10 space straight x 80 end root space equals 40 space straight m divided by straight s
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What are different units of energy?

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(v) Calorie.

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What is watt?

SI unit of power is Watt. 
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Work done is said to be one joule if one newton of  force displaces the body through a distance of one meter in the direction of applied  force .
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