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CBSE Class 11-science Answered

Kunal’s heart beats 72 times in one minute. If the length of second hand of watch is 4.5 cm. Find the distance travelled by the tip of second’s hand of watch when Kunal’s heart beats 300 times.
Asked by Topperlearning User | 31 May, 2016, 08:49: AM
answered-by-expert Expert Answer

Heart beats 72 times in 1 minute

 
Therefore it beats 300 times in 1 over 72 cross times 300 space m i n u t e s equals 25 over 6 space m i n u t e.
N o w space 25 over 6 space m i n u t e equals 25 over 6 cross times 60 space s e c o n d s equals 250 space s e c o n d s.
Now angle swept by seconds hand 250 x 6= 1500 degrees

1500 degree equals straight pi over 180 cross times 1500 equals fraction numerator 25 straight pi over denominator 3 end fraction space r a d i a n
 
The distance travelled is given by l equals r theta 
 
N o w space theta equals fraction numerator 25 straight pi over denominator 3 end fraction comma space r equals 4.5 space c m 
l equals 4.5 cross times fraction numerator 25 straight pi over denominator 3 end fraction equals 1.5 cross times 25 straight pi equals 1.5 cross times 25 cross times 3.14 equals 117.75 space cm
 
Answered by | 31 May, 2016, 10:49: AM

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