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CBSE Class 9 Answered

Please help me int the following quesitons.
Asked by | 07 Mar, 2013, 11:16: AM
answered-by-expert Expert Answer
1.  
A man of mass 62kg
climbs up a stair case of 65 steps ,height of each step is 20cm,
time 12s.
his power=P=mgh/t
               =(62x10x65x20)/(100x12)

              =371.6W
 
2)The kinetic energy of an object moving with a velocity of 5m/s is 25J.
 
1/2 mx 5x5=25
m=2kg
 
 
What will be its kinetic energy when its velocity is made (i)two times (ii)three times?
 
as KE is proportional to square of vel, so :
 

its velocity is made (i)two times, KE will be 4 times.
 
  (ii)three times: then KE will be 9 times.            
Answered by | 07 Mar, 2013, 11:31: AM

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