This is due to the law of inertia, an object at rest stays at rest and an object in motion stays in motion unless acted upon an unbalanced force.
So when you are traveling in a car I'm assuming the driver Gina is wearing her seatbelt, when Gina hits her brakes that is the "unbalanced force". By hitting the brakes Gina will also nudge forward but is stopped by her seatbelt from going too far forward. The teddy bear is not so lucky and since he's not wearing a seatbelt he is propelled forward hitting the dashboard. Poor Teddy.