Tagged Questions
3
votes
1answer
88 views
Calculating the path of a ball with spin moving across a table
A ping pong ball is rolling over a smooth (but not frictionless) table. During its travel, a clockwise spin is placed on the ball. The ball's path is changed to move to the right (in perspective from ...
1
vote
3answers
354 views
Conservation of energy in objects at terminal velocities
In vacuum, object free falling under gravity, the sum of Gravitational Potential Energy(GPE) and Kinetic Energy (KE) is a constant. The GPE is a decreasing side of a quadratic and KE is a increasing ...
3
votes
1answer
547 views
Where does the lost energy go in a rubber band powering a rotating shaft?
Okay, I'm no physics whiz, and this has me stumped. You know those toy airplanes you can get with the rubber-band driven propellers? You twist the propeller a bunch of times, and this stores ...
0
votes
0answers
67 views
How to control heavy ball in x and y direction? [closed]
I'm trying to build a device that holds a rather heavy ball and I want to be able to control it's "movement" in the X and Y directions (they are horizontal as well as orthogonal).
My current ...
2
votes
2answers
482 views
Conservation of angular momentum in helicopter
I have a small RC-controlled toy helicopter with removable tail rotor.
Suppose I remove the tail rotor, hold the tail with my hand, start the rotor until it moves with constant angular velocity and ...
1
vote
1answer
222 views
What conditions must be met for a ball to roll perfectly down an incline without slipping?
What conditions must be met for a ball to roll perfectly down an incline without slipping? A mathematically rigorous definition, please.
I honestly don't know where to begin with answering this ...
3
votes
1answer
386 views
When is the principle of virtual work valid?
The principle of virtual work says that forces of constraint don't do net work under virtual displacements that are consistent with constraints.
Goldstein says something I don't understand. He says ...
3
votes
1answer
425 views
Rope wrapped around a cylinder
If a rope is wrapped aound a cylinder what is the relationship between the amount of wrap and the ability to resist slipping off of the cylinder? An example would be if I had a 180 degree wrap and ...
2
votes
1answer
902 views
Rolling resistance and static friction
I am a bit confused about the relation between rolling resistance and static friction.
I have often heard that it is the static friction that lets the wheel roll. Consider the following two cases:
...
2
votes
1answer
207 views
Thermal energy generated due to loss in kinetic energy when observed from two different frames of reference
A body is moving with a velocity $v$ with respect to a frame of reference $S_1$.
It bumps into a very heavy object and comes to rest instantaneously, its kinetic energy
$$\frac{1}{2}mv^2$$
as ...
-1
votes
4answers
294 views
Whats wrong with this perpetual machine?
Consider a cube of mass M resting on a rough surface such that the coefficient of friction between the cube and the surface is K. So in order to just slide the cube I need to apply a minimum force of ...
