When is a vernier callipers said to be free from zero error ?
A vernier calipers is said to be free from zero error, if the zero mark of the vernier scale coincides with the zero mark of the main scale.
A boy uses a vernier callipers to measure the thickness of his pencil. He measures it to be 1.4 mm. If the zero error of vernier callipers is + 0.02 cm, what is the correct thickness of pencil ?