A student pushes a book across a classroom table. Which of the following statements best explains the difference between the amount of force needed to start the book moving and the amount of force needed to keep it moving?
A)Less force is needed to start the book moving, because there is less friction than when it is already moving.
B)Less force is needed to start the book moving, because there is less potential energy in the table than in the book.
C)More force is needed to start the book moving, because there is more potential energy in the table than in the book.
D)More force is needed to start the book moving, because there is more friction than when it is already moving.

Question

Quizplus · Accepted Answer

Static friction, which must be overcome to start an object moving, is generally greater than kinetic friction, which is the frictional force encountered when an object is already in motion.

A Student Pushes a Book Across a Classroom Table