You are here:

# Physics/Dryer Door - closes easily when swung

Question
Hi,

Why does the dryer door close more easily when swung/slammed (as opposed to pushing on handle slowly)?  I understand that the hinge is a lever.

*  Swinging/slamming of door - hand no longer on door slams door easier
*  Slow pushing of door - hand continuously pushing on door is harder

*  Is swinging door accelerating or at constant velocity?
*  Is swinging door increasing in momentum?
*  Is there air pressure difference from swinging of door (wind?)?
*  I assume swinging door requires less force?
*  Is slowly pushing door with hand requiring more force to move weight of door AND weight of dryer (resistance)?
*  Is there torque (I don't understand this well)?

Thanks,
Elizabeth

The swinging door, the way you describe it, is moving at constant angular velocity.  It is technically accelerating, since it is swinging and not moving in a straight line.  Its momentum is constant.  Of course there is air resistance.  Swinging might use more or less force, depending on how it is pushed to get it swinging.  The next to last question has no real answer, since there's no way to quantify the resistance of the dryer's door stop.  Torque is applied to get anything to rotate, so yes there is a torque to get it swinging.  After that, the hinges will provide very little torque.  Torque will also be present when it slams shut (stops swinging).

Physics

Volunteer

#### Dr. Stephen O. Nelson

##### Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

##### Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.