Q 8.31: Two objects interact with each other and with no other objects. Initiall
ID: 1605354 • Letter: Q
Question
Q 8.31:
Two objects interact with each other and with no other objects. Initially object A has a speed of 6 ms/6 ms and object B has a speed of 5 ms/5 ms . In the course of their motion, they return to their initial positions. Then A has a speed of 2 ms/2 ms and B has a speed of 1 ms/1 ms . We can conclude (Select all that apply)
A
mechanical energy was decreased by nonconservative forces.
B
mechanical energy was increased by nonconservative forces.
C
the potential energy is unchanged from the beginning to the end of the trip.
D
mechanical energy was decreased by conservative forces.
E
mechanical energy was increased by conservative forces.
The answers are A & C
Could you please explain about C?
Explanation / Answer
Kinetic energy is dependent upon the velocity and potential energy is dependent upon the configuration of the particles in the system. The mechanical energy is the sum of kinetic energy and potential energy.
As the particles come back to their initial configuration the speed of particle is decreased by some non conservative force such as frictional force or electrostatic force thus their is a decrease in kinetic energy and hence the mechanical energy of yhe system decrease. The potential energy which is dependent upon conservative force remains the same as the particles come back to their initial position. Thus the potential energy remains the same as it is a function of position. Hence A and C are correct.
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