Sticky Collisions

A sticky collision(inelastic collision) is when two objects collide together forming one bond and changing kinetic energy.  The equation for this is:

m1V1 + m2V2 = (m1 +m2)Vf.

The initial mass multiplied by the initial velocity of vehicle one added to the initial mass multiplied by the velocity of vehicle two should equal to the final mass of vehicle one plus the final mass of vehicle two multiplied by the final velocity.

Let's say you have a parked car and another plows into it from the back.  Both cars would move off in the same direction connected together.


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If a car hits a brick wall, that would cause an inelastic collision as opposed to a head-on collision where the two cars would bounce back which is called an elastic collision.

Here's a visual equation so you can see how this collision works.

A car is traveling at a velocity of 10 m/s with a mass of 700 kg.  It hits a brick wall, which has a mass of 5000 kg and, obviously, no velocity. 

Given:   X1:  m = 700 kg.

                       V = 10 m/s

             X2:  m = 5000 kg

                      V = 0 m/s

Now you can find the final velocity of the car after the collision.

(700kg)(10m/s) + (5000kg)(0 m/s) = (700kg + 5000kg)(Vf)

7000 kg x m/s + 0kg x m/s = (5700 kg)(Vf)

The final velocity of the brick wall and the car = 1.228 m/s.