Abig defensive lineman picks up a fumbled football and begins rumbling toward the end zone. his mass is 150 kg, and his velocity is 5.0 m/s, west. a brave wide receiver, whose mass is 90 kg, must stop that lineman and he is right in the lineman's path, so it has to be a head-on collision. how fast must the wide receiver be running if he wants to drop the lineman in his tracks and save the day?

Explanation:

The linear momentum during this collision must be conserved, which means that momentum before and after the collision must be the same.

We have a big defensive lineman of mass and velocity going in what we will call the positive direction, and a wide receiver of mass and velocity which we don't know. Since the collision is head on, momentum before the collision will be

After the collision, the receiver drops the lineman in his tracks, which means they come to a stop, so the momentum is null, and since this momentum must be equal to the one before the collision we have:

Which means:

So for we have:

where the negative sign indicates its opposite to our positive direction (of the big defensive lineman).

this could be newton#'s law of cooling. the cooling curve is exponential