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Saturday, 15 December 2012

Q.No.2.19: - Identify true or false statements and explain the reason. (a) A body in equilibrium implies that it is neither moving nor rotating. (b) If coplanar forces acting on a body form a closed polygon, and then the body is said to be in equilibrium.


Q.No.2.19: - Identify true or false statements and explain the reason.
(a) A body in equilibrium implies that it is neither moving nor rotating.
(b) If coplanar forces acting on a body form a closed polygon, and then the body is said to be in equilibrium.
Ans: -
(a)   This is false statement since a body may be in equilibrium if it is moving with uniform velocity.
(b)  This is a correct statement since a closed polygon represents zero vector sum of forces and this is the 1st condition of equilibrium.
Q.No.2.20: - A picture is suspended from a wall by two strings. Show by diagram the configuration of the strings for which the tension in the strings will be minimum.
Ans: - The tension in the suspension strings will be minimum for the configuration shown in the figure. In this case, the tension in each string will be half that of weight.
                           2T = W                     or               T W/2

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