Question

A ball of mass 0.1 kg is suspended by a string. It is displaced through an angle of 60° and left.
When the ball passes through the mean position, the tension in the string is
(A) 19.6 N
(B) 1.96 N
(C) 9.8 N
(D) Zero​

Answer 1

Answer:

$<marquee behavior = move bgcolor =yellow ><h1 > Option C</h1 ></marquee >$..................

Answer 2

Given that,

Mass of ball = 0.1 kg

Angle = 60°

According to diagram,

changes length $l'=l-l\cos\theta$

We need to calculate the velocity

Using formula of energy

$\dfrac{1}{2}mv^2=mgl(1-\cos\theta)$

$\dfrac{mv^2}{l}=2mg(1-\cos\theta)$....(I)

We need to calculate the tension in the string

Using balance equation

$T-mg=\dfrac{mv^2}{l}$

Put the value from equation (I)

$T=mg+2mg(1-\cos\theta)$

Put the value of angle

$T=mg+2mg(1-\cos60)$

$T=mg+2mg\times\dfrac{1}{2}$

$T=2mg$

Put the value into the formula

$T=2\times0.1\times9.8$

$T=1.96\ N$

Hence, The tension in the string is 1.96 N.

(B) is correct option