Problem 5-51 Force and Kinematics - Part 2

The oriental rat flea, a major carrier of bubonic plague, can jump a vertical distance more than 100 times its body length. (Imagine if you could do that!) During the initial phase of the jump, the flea is in contact with the ground for a typical time of \(1.2 \;ms,\) and has an average upward acceleration of \(1.0 \times 10^3 m/s^2\) (about \(100 \;g\)). The mass of an average oriental rat flea is \(2.1 \times 10^{-7} kg.\) Neglect air resistance.

(a) During the initial phase, of the jump, what is the magnitude of the resultant force on the flea?
(b) Draw a FBD for the flea in (a). What object exerts the upward force on the flea?
(c) After the flea has lost contact with the ground, what is the resultant force (magnitude and direction) on it?
(d) How high does the flea jump?

Accumulated Solution

\(F = ma = (2.1\times 10^{-7})(1.0 \times 10^3 ) = 2.1\times10^{-4}N\; \text{(answer to part (a))}\)

Which of the following is the FBD for the flea in part (a)?

Possible free body diagrams A, B, C, D.