Q.

A stone of mass 900 g is tied to a string and moved in a vertical circle of radius 1 m, making 10 rpm. The tension in the string when the stone is at the lowest point is (if π2 = 9.8 and g = 9.8 m/s2)               [2024]

1 17.8 N  
2 8.82 N  
3 97 N  
4 9.8 N  

Ans.

(4)

Given that, m=900 gm=9001000 kg=910 kg

r=1 m

ω=2πN60=2π(10)60=π3 rad/sec

T-mg=mrω2    T=mg+mrω2

T=910×9.8+910×1(π3)2

           =8.82+910×π29=9.80 N