Q.

A small block of mass 100 g is tied to a spring of spring constant 7.5 N/m and length 20 cm. The other end of spring is fixed at a particular point A. If the block moves in a circular path on a smooth horizontal surface with constant angular velocity 5 rad/s about point A, then the tension in the spring is              [2023]

1 0.50 N  
2 0.75 N  
3 1.5 N  
4 0.25 N  

Ans.

(2)

Let extension in length of spring be x.

Radius of circle, r=0.2+x

kx=mω2r

7.5x=(110)(5)2(0.2+x)

152x=52(x+15)

x=110

 Tension in spring=kx=7.5×110=0.75 N