2. Conceptual questions about the work-energy theorem. Reminder: If your explana

Question

2. Conceptual questions about the work-energy theorem. Reminder: If your explanation doesn't include a fact, equation, or calculation, it is wrong. You must answer in three sentences or fewer, though equations and diagrams may be used as well (a) An object is attached to a spring. In case A, the spring is compressed by 1 cm. In case B, the spring is compressed by 2 cm. By what factor is the energy stored in the spring greater in case B? A 2-kg object accelerates as a net force acts on it. During the 5 seconds this force acts, the object changes its velocity from 3 m/s east to 7 m/s west 3 ms- seconds later:- 7 m/s A student states: "The change in kinetic energy of this object during these 5 seconds was 40 J, and thus the work done on this object by the net force during this period was also 40 J." What, if anything, is wrong with this statement? If something is wrong, identify it, and explain how to correct it. If this statement is correct, explain why.

Explanation / Answer

a) for a spring , as the energy stored is given as U = 0.50 * k * x^2

hencem , when the compression or expansion is doubled , the stored energy will be 4 times ,therefore , the energy stored in case B is 4 times larger.

b)

for the object , change in kinetic energy = 0.50 * 2 * (7^2 - 3^2)

change in kinetic energy = 40 J

NOw, according to work energy theorum , net work done on the object is equal to the change in kinetic energy .
hence , the student is correct.

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