JEE MAIN - Physics (2020 - 6th September Morning Slot - No. 7)
An insect is at the bottom of a hemispherical ditch of radius 1 m. It crawls up the ditch but starts
slipping after it is at height h from the bottom. If the coefficient of friction between the ground and
the insect is 0.75, then h is :
(g = 10 ms–2)
(g = 10 ms–2)
0.45 m
0.60 m
0.20 m
0.80 m
Explanation
_6th_September_Morning_Slot_en_7_1.png)
For balancing mgsin $$\theta $$ = f
mgsin $$\theta $$ = $$\mu $$mgcos $$\theta $$
$$ \Rightarrow $$ tan $$\theta $$ = $$\mu $$ = $${3 \over 4}$$
_6th_September_Morning_Slot_en_7_2.png)
h = R – R cos$$\theta $$
= R - R$$\left( {{4 \over 5}} \right)$$ = $${R \over 5}$$
$$ \therefore $$ h = $${R \over 5}$$ = $${1 \over 5}$$ = 0.2 m
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