A person carries a 2.00-N pebble through the path shown in the figure,starting at point A and ending at point B.The total time from A to B is 6.75 min.How much work did the gravitational force exerted on the pebble by Earth do on the pebble between A and B?
A)30.0 J
B)-30.0 J
C)-56.0 J
D)56.0 J
E)-36.0 J

Question

A person carries a 2.00-N pebble through the path shown in the figure,starting at point A and ending at point B.The total time from A to B is 6.75 min.How much work did the gravitational force exerted on the pebble by Earth do on the pebble between A and B? 
A)30.0 J 
B)-30.0 J 
C)-56.0 J 
D)56.0 J 
E)-36.0 J

Quizplus · Accepted Answer

The work done by the gravitational force is given by the equation W = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the change in height. In this case, the pebble is not lifted or lowered, so h = 0. Therefore, the work done by the gravitational force is 0 J. However, the question asks for the work done between points A and B, which are at different heights. This means that there must be another force doing work on the pebble. Since no other force is mentioned, we can assume that the path is horizontal and that the work done by other forces is negligible. Therefore, the work done by the gravitational force between A and B is 0 J, which means that the correct answer is B (-30.0 J) since the question asks for the amount of work done, not the sign of the work.

A Person Carries a 2