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**Impulse -- I am suspecting a wrong answer on the key.**

A 2.4-kg ball falling vertically hits the floor with a speed of 2.5 m/s and rebounds with a speed of 1.5 m/s. What is the magnitude of the impulse exerted on the ball by the floor?

* 9.6N/s

* 2.4N/s

* 6.4N/s

* 1.6N/s

* 1.0N/s

Answer key says

**9.6N/s**

My calculations say

**2.4N/s**

Impulse = ∆Momentum

∆Momentum = mv(Initial) - mv(final)

∆Momentum = (2.4kg)(2.5m/s) - (2.4kg)(1.5m/s)

∆Momentum = 6 - 3.6 =

**2.4 N/s**

What is the right way of doing this?