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 gravity do on the rock 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 gravity do on the rock 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 gravity is given by the formula W = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the change in height. Since the pebble ends at the same height as it started (same horizontal line), there is no change in height and therefore no work done by gravity. The answer must be negative since the pebble is moving upwards against the force of gravity, so the only possible answer is B.

A Person Carries a 2