What Must Superman's Initial Velocity Be to Save the Falling Student?

[ash312]

Homework Statement

A student is determined to test the law of gravity for himself. He steps off a skyscraper 320m high, stopwatch in hand, and starts his free fall. Five seconds later, superman arrives at the scene and dives off the roof to save the student. What must superman's initial velocity be in order to catch the student just before the student reaches the ground? Assume superman obeys the laws of physics like any other free falling objects

Homework Equations

v2^2 = v1^2+2aΔd

The Attempt at a Solution

I used the formula above to calculate that the student will be traveling at 79m/s just before he hits the ground. But i think i have the wrong approach

 

[PeterO]

Homework Statement

A student is determined to test the law of gravity for himself. He steps off a skyscraper 320m high, stopwatch in hand, and starts his free fall. Five seconds later, superman arrives at the scene and dives off the roof to save the student. What must superman's initial velocity be in order to catch the student just before the student reaches the ground? Assume superman obeys the laws of physics like any other free falling objects

Homework Equations

v2^2 = v1^2+2aΔd

The Attempt at a Solution

I used the formula above to calculate that the student will be traveling at 79m/s just before he hits the ground. But i think i have the wrong approach

That is the correct speed for the student - or very close; depends what value for g you used.