CBSE Class 9 Answered
9. A girl moves along a circular path of radius 14m. What is her distance and displacement when she completes: (a) Half round (b)Two rounds
Asked by tognosigno | 02 May, 2020, 11:05: AM
Radius of circular path, r = 14 m
a) Half round
Distance when girl completes half round
We know,
circumference of circle = 2∏r
Thus circumference of semicircle (half circle) = ∏r
Hence,
![D i s tan c e space w h e n space g i r l space c o m p l e t e s space h a l f space r o u n d space equals space 22 over 7 cross times 14 space equals space 44 space m space
D i s p l a c e m e n t space equals space d i a m e t e r space o f space t h e space c i r c l e space equals space 2 space cross times r equals 2 cross times 14 space equals space 28 space m space](https://images.topperlearning.com/topper/tinymce/cache/a57fada3172ea58f0044dea40b3da3d6.png)
b) Two rounds
![W h e n space g i r l space c o m p l e t e s space t w o space c i r c l e s space
D i s tan c e space t r a v e l l e d space b y space h e r space o n space c o m p l e t i n g space t w o space r o u n d s space o f space c i r c u l a r space p a t h space equals space 2 space open parentheses 2 pi r close parentheses space equals space 2 space cross times open parentheses 2 cross times 22 over 7 cross times 14 close parentheses space equals space 176 space m space
D i s p l a c e m e n t space w h e n space g i r l space c o m p l e t e s space t w o space r o u n d s space o f space c i r c u l a r space t r a c k space equals space 0 space
space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space.... space left parenthesis B e c a u s e space s h e space c o m e s space t o space t h e space i n i t i a l space p o s i t i o n. space S o space t h e space m i n i m u m space l e n g t h space b e t w e e n space f i n a l space a n d space i n i t i a l space p o s i t i o n space i s space z e r o. space H e n c e space d i s p l a c e m e n t space i s space z e r o right parenthesis](https://images.topperlearning.com/topper/tinymce/cache/536925619767483fee794c04ca107f16.png)
Answered by Shiwani Sawant | 02 May, 2020, 13:20: PM
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