13. A student runs two times around a running path at a local park. Each lap is 3 km. The student completes the first lap in 20 minutes. The student then sits
on a bench and rests for 5 minutes before completing the second lap in 25
minutes. Which graph best represents the student's motion?

ek = (m·v2) / 2

v - velocity of system after the collision

m = m1 + m2

ek = (m1 + m2) ·v2/2

ek = (200 + 250) ·2,32/2 = 450·5,29/2 = 1190,25 j

the correct answer is moro reflex. this is usually witnessed in infants normally up to the age of 4-5 months (in some cases maybe more)  

it is caused by a sudden loss of support that makes the baby feel as if he or she is falling or is going to fall and hence the flinging of the arms and crying.