Impulse Response of a simple structure

Hi everyone,

I would like to simulate a simple structure under the action of an impulsive force.
The structure is a free-clamped cantilever, where the impulse force is applied at the free end.

The stationary study gives no problem at all, so I define magnitude and direction of the static load and I obtain the displacement (or other mechanical parameters) of the structure.

However I have no idea of how to define an impulsive load.
I set a Time dependent study, but the load keeps being static.

I'm using comsol 4.3.

Thanks in advance to whoever is going to help :)
(I'm quite sure it's pretty easy to do, even though I couldn't find any tutorial on this matter).