Elevator Motion
Elevators are contraptions made for convenience, especially for people who travel several floors at a time inside a tall building. You may have noticed that it feels no different inside an elevator in the middle of its journey up or down than it feels to be standing on a stationary ground (one that is not moving). This is because the elevator is not accelerating during the middle portion of its motion between floors.
Elevators come in handy when traveling many floors at a time.
Acceleration is a change in velocity over a period of time. Actually, this is specifically known as tangential acceleration (there are other forms of acceleration, namely that due to rotational motion, which may be discussed in a future post). The elevator’s motion can be broken down into three stages:
- Start: the elevator accelerates from zero velocity (so you can step into the elevator safely) to its nominal travel speed.
- Middle: the elevator travels at its nominal travel speed without speeding up nor slowing down.
- End: the elevator decelerates (you can think of this as backwards acceleration) from its nominal travel speed to zero velocity (so you can step out of it and onto your destination floor safely).
The reason why you feel a force acting on your feet when the elevator starts up in the beginning and slows down at the end is because the elevator is accelerating during those stages. Newton’s second law states that force is directly proportional to acceleration. So, even if the elevator is moving very fast but at a constant speed, you will not feel an external force acting on you because there is no acceleration.
This same notion of not feeling anything different inside a moving vehicle (such as an elevator car) when there is no acceleration can also be applied to riding in a automobile on the road. When driving on the straight highway at a constant speed, you feel no external force acting on you and you sit comfortably. On the other hand, when you accelerate or decelerate your car, you feel a force pushing you back against the seat (during acceleration, or speeding up) or forward (during deceleration, or slowing down). Also, the force that you feel is directly proportional to the acceleration of the car, so if you speed up very quickly (which happens to not be very fuel-efficient) then you will feel a larger force.
Until next time, may your vehicular travels be smooth and comfortable without any jerky accelerations.
Leave a Comment