to sharpen a knife using a grinding stone of radius 7/44 m it should rotate at 120rpm. if the knife is pressed towards grinding stome with a force of 100N. Then power of the water is ?
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Power = force.velocity
Given , Force = 100N
Radius grinding stone , r = 7/44 m
frequency = 120rpm , means frequency is 120 rotation per minutes
so, angular velocity , ω = 2π × frequency
= 2π × 120/60 rad/sec = 4π rad/sec
Now, linear velocity, v = ωr , here r is radius of grinding stone .
v = 4π × 7/44 = 4 × 22/7 × 7/44 = 2 m/s
Hence, power = force × velocity
= 100 × 2 = 200 watt
Given , Force = 100N
Radius grinding stone , r = 7/44 m
frequency = 120rpm , means frequency is 120 rotation per minutes
so, angular velocity , ω = 2π × frequency
= 2π × 120/60 rad/sec = 4π rad/sec
Now, linear velocity, v = ωr , here r is radius of grinding stone .
v = 4π × 7/44 = 4 × 22/7 × 7/44 = 2 m/s
Hence, power = force × velocity
= 100 × 2 = 200 watt
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