Its called the Phase Transition. Im assuming your asking what is it called when matter transitions between solid liquid and gas.
Answer:
1.23 m/s
Explanation:
The kinetic energy of the sprinter is:
KE = 0.5 * m(s) * v²
KE = 0.5 * 77 * 7.5²
KE = 2165.63 J
If the KE of the sprinter and the KE of the elephant are equal, hence:
2165.63 = 0.5 * m(e) * v²
2165.63 = 0.5 * 2850 * v²
=> v² = 1.52
v = √(1.52)
v = 1.23 m/s