How much net work (in J) is required to triple her speed?

A 62.1 kg runner has a speed of 3.70 m/s at one instant during a long-distance event. The runner's kinetic energy is 425.07 Joules.

?2018-12-07T05:56:46Z

Kinetic enregy depends on the square of the velocity, so to raise the speed to its triple value, the
kinetic energy increases by a factor of 3² = 9.
The net work required is therefore 8 times the original kinetic energy