Important Questions on Measurement of Length and Motion
A plano-convex lens of unknown material and unknown focal length is given. With the help of a spherometer we can measure the 
The commutator bracket is expanded as Why a foot-step cannot be used as a standard unit of length? Discuss why non-standard units cannot be used for accurate measurements. Why did people in ancient times realise the need for some fixed quantity of measurement? Name two body parts of a person which can be used as units of measuring length. Which of the following measures was used in ancient times? What is cubit? Explain why cubit cannot be used as a standard unit of length. The footstep is an unreliable measure of length because Name any two measures used in ancient times. Elaborate the ways in which people in ancient times used to measure length. Also mention the importance or need of accurate measurement. How did people measure the length and weight of things in olden days? What did people in ancient times use to measure length? Explain why, hand-span cannot be used as a standard unit of length. The length between the tip of the finger and elbow is called _____. Why cannot a foot length or cubit be used as a standard unit of length? What did people in ancient times use for measurement? The hand span is a reliable method of measurement of length. Explain with examples how people measured length in ancient times. 
