Question

Can anyone help with part b of this question? I really appreciate your help. Thank you!

The diagram from the previous page is reproduced at right for your convenience. Is deltaK SB, the change in kinetic energy of system SB, positive, negative, or zero? Explain. Is deltaU SB, the change in potential energy of system SB, positive, negative, or zero? Explain. Is W net ext, SB, the net work done on system SB by external forces, posiitve, negative, or zero? In either case, explain. Consider the system B: the block alone. For each hoprizontal force acting on system B, specify whether the work done by the force is positive, negative, or zero. Explain. Is deltaKB, the change in kinetic energy of system B, positive, negative, or zero? Explain. Is deltaUB, the change in potential energy of system B, positive, negative, or zero? Explain. Is W net ext, B, the net work done on system B by external forces, positive, negative, or zero? In either case, explain.

Answer 1

(b)
(1) Work done by the force must be +ve because
work done is given by = Force*displacement*Cos0 = F.dCos0
that means the force and displacemnt is in same direction.
hence the work done must be +ve.
(2) We know that
Work done = change in kinetic energy
Work done = Final energy - Initial kinetic energy
(Since initial kinetic energy is Zero )
Work done = Final kinetic energy
Since the work done is +ve therefore Kinetic energy would be +ve.
(3) Since there is no change in the height therefore the potential energy will be ZERO.
(4) Work done on system by external force on the block will be negative.