We can feel the change in anything when we can feel it. Because we can sense acceleration, we can also feel a jerk. Which is undeniably true, but there is another sense in which jerks may have a direct impact on our physiology in some situations. For example, if a car starts to skid out of control, its driver will feel the effect through his or her seat belt. The driver's body will react in order to maintain safety. If the belt isn't tight enough, it won't be able to do its job and protect against injury. When something feels like a jerk, that means that your brain gets the message and reacts accordingly. If you were sitting in your car when this happened, you would probably feel anxious or afraid. Your body would be preparing for an accident. This is why jerks can affect us physiologically. Our brains interpret these sensations as dangerous and tell our bodies to prepare for them. This could result in increased heart rate, sweating, shaking, or nausea. However, there is another type of jerk that doesn't involve danger and that most people don't experience. A mechanical jerk happens when a vehicle makes frequent sudden movements back and forth. These might be repeated bumps in a road or hills in close succession. In this case, our brains don't notice the movement and cannot communicate with our bodies to warn them.