Work and Changes in Kinetic Energy I tried rotating it, but it won\'t rotate. So
ID: 1589829 • Letter: W
Question
Work and Changes in Kinetic Energy
I tried rotating it, but it won't rotate. Sorry!
In experiment 1, two hands push identical blocks of mass m toward each other across a level, frictionless surface with a constant force of magnitude F_0 over the interval from t_1 to t_2. In this problem, you will consider 4 other experiments in which the setup differs from that in experiment 1. In each experiment, both blocks start from rest at time t_1 on a level, frictionless surface; both hands exert the same magnitude force, Fp, over the interval from t_1 to t_2; and the blocks do not run into each other during this interval. In each experiment, consider the net work done during the interval from t_1 to t_2 by external forces on the system that consists of the blocks and any spring or rod that may be connecting them. In experiment 2, the hands push in the same direction. For the interval from t_1 to t_2, is the net external work on the system of the two blocks in experiment 2, greater than, less than, or equal to that in experiment 1? Explain. In experiment 3, the blocks are connected by a spring. The spring is initially neither stretched nor compressed. For the interval from t_1, to t_2, is the net external work on the system of the two blocks and the spring in experiment 3 greater than, less than, or equal to that in experiment 1? Explain. In experiment 4. the mass of one of the blocks is m/2. For the interval from t_1 to t_2, is the net external work on the system of the two blocks in experiment 4 greater than, less than, or equal to that in experiment 1 ? Explain. In experiment 5, the blocks are connected by a rigid rod (i.e., a rod that can not compress). For the interval from t_1, to t_2, is the net external work on the system of the two blocks and the rod in experiment 5 greater than, less than, or equal to that in experiment 1? Explain.Explanation / Answer
Theory:
From the above theory now we can easily answer to the questions:
a) The change in kinetic energy will be same and since there is only one force acting hence the work done will same (equal) as experiment 1.
b) Considering the spring force as the internal force, the net work done on the system (by both internal and external forces) is same as in experiment one, but here the spring force is doing overall negative work hence the external work done will be greater than that of the experiment 1.
c) Here the impulse is same as exp 1 and so as the change in momentum but mass is half then change in kinetic energy will be more than that of experiment 1 hence the net work done by external force will be greater than that of 1.
d) Here no motion is possible then the work done will be zero, hence less than that of exp 1.
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