Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

As shown in the figure below, a light string that does not stretch changes from

ID: 1901920 • Letter: A

Question

As shown in the figure below, a light string that does not stretch changes from horizontal to vertical as it passes over the edge of a table. The string connects m1, a 3.60 kg block, originally at rest on the horizontal table at a height 1.30 m above the floor, to m2, a hanging 2 kg block originally a distance d = 0.980 m above the floor. Neither the surface of the table nor its edge exerts a force of kinetic friction. The blocks start to move from rest. The sliding block m1 is projected horizontally after reaching the edge of the table. The hanging block m2 stops without bouncing when it strikes the floor. Consider the two blocks plus the Earth as the system.

(d) Is the energy of the system when it is released from rest equal to the energy of the system just before m1 strikes the ground?

(e) why or why not?

Explanation / Answer

(d) No. (e)Because before m1 hits the ground, m2 hits it. Ground applies an external force on it. Principle of conservation of energy is not valid when there is an external force.