[two waves] pass a point [every second]... The answer is in the question (B)
Complete Question:
The elastic energy stored in your tendons can contribute up to 35 % of your energy needs when running. Sports scientists have studied the change in length of the knee extensor tendon in sprinters and nonathletes. They find (on average) that the sprinters' tendons stretch 43 mm , while nonathletes' stretch only 32 mm . The spring constant for the tendon is the same for both groups, . What is the difference in maximum stored energy between the sprinters and the nonathlethes?
Answer:
Explanation:
Sprinters' tendons stretch,
Non athletes' stretch,
Spring constant for the two groups, k = 31 N/mm = 3100 N/m
Maximum Energy stored in the sprinter,
Maximum energy stored in the non athletes,
Difference in maximum stored energy between the sprinters and the non-athlethes:
Since Astronaut and wrench system is isolated in the space and there is no external force on it
So here momentum of the system will remain conserved
so here we can say
initially both are at rest
so here plug in all values
so here the astronaut will move in opposite direction and its speed will be equal to 0.20 m/s