Two students, Alice and Bob, carry out an experiment to measure the speed of
cars. Alice paces out the distance between two lamp posts.
She records:
'Distance between lamp posts = 20 paces'
Bob starts to count when a car passes the first lamp post. He stops
countingwhen he thinks it has passed the second lamp post.
He records:
'My estimate for the time taken for the car to pass between the two lamp posts = 3'
Give three ways the students could improve their experimental procedure.