Question

A baseball is hit high into the upper bleachers of left field. Over its entire flight the work done by gravity and the work done by air resistance respectively are:
A. positive; positive
B. positive; negative
C. negative; positive
D. negative; negative
E. unknown since vital information is lacking

Answer 1

Answer:

B. positive; negative.

Explanation:

From the viewpoint of Principle of Energy Conservation and Work-Energy Theorem, we notice that gravity represents a conservative force, associated with gravitational potential energy, whereas air resistance is a non-conservative force, associated with dissipated work. Therefore, the work done by gravity is positive and work done by air resistance is negative. Therefore, the correct answer is B.