A heavy bird sits on a clothesline. Will the tension in the clothesline be greater if the line sags a lot or if it sags a little?
ANSWER: When the bird sits at the clothesline, the line bends downwards because of the weight of the bird. The bending causes a tension in the wire or string. The tensions at the two sides of the bird actually balance the weight of the bird, so everything could be in equilibrium. As the mass of the bird is constant and the force due to the weight is also constant, the tension will be same whether the string bends more or less. Only the direction of the tension forces change. It depends on the quality of the clothesline that how much it would bend. If a more massive bird sits on it and the line bends more then the tension increases. Generally people think that, if the bending of line is more then the tension is also more. This is not certainly true, as the tension forces here balance the weight only. And until the weight increases, the tension does not change