Question 1
A smooth pebble, made from uniform rock, has the shape of an elongated sphere as shown in Fig. 1.1.
Fig. 1.1
The length of the pebble is L. The cross-section of the pebble, in the plane perpendicular to L, is circular with a maximum radius r.
A student investigating the density of the rock makes measurements to determine the values of L, r and the mass M of the pebble as follows:
State the name of a measuring instrument suitable for making this measurement of L.