As per observations, I understand that the length and shape of shadows does change with the position of the Sun.
The light is coming from Sun at an angle to earth during morning and late afternoon. Therefore if an object is placed standing in the sun, greater surface of the object is blocking the sunlight, more sun rays are blocked and a bigger shadow is formed. At midday, the sun rays are coming almost straight down on earth. So if the object is placed in the same position in the Sun, less surface of the object is blocking the light, less sun rays are blocked and so the shadow is small.

My hypothesis  regarding the change of length and shape of shadows with the position of the sun is correct.