Weightlessness in a common swing

[skazis]

Hi,

Our sensation of weight is given by gravity together with normal forces. It is said that in a swing you'll feel weightless at the top of the ride (180 degrees), because there is no seat that gives you normal force. But from my experience there is something strange even before 180 degrees, when swing stops and goes other way around, just like a free fall. It might be just because after 90 degrees there is no force projection on the seat as well? And this "180 degree fact" is slightly wrong?

Skazis

 

[PowerBuilder]

Interesting. I must admit I have been to numerous parks with my kids...used the swings and thought about what's going on as well as watch them playing on them.

 

[HallsofIvy]

When you swing, you will feel a centripetal force pressing you against the seat (more correctly, pressing the seat against you) but that has nothing to do with gravity- you would feel it even if you were "swinging" in a weightless environment. Of course, in that case your swing would just keep going in a circle.

 

[willem2]

You feel a normal force, because of the centripetal acceleration needed to make you follow a circular arc, and because of the radial component of gravity.

When the swing is a its highest point, there is no centripetal acceleration and there's only the force of gravity.

If the swing makes an angle A with the vertical, the force of gravity mg on you will have a component mg sin (A) which will accelerate the swing tangentially, but will not be felt by someone on the swing. There is also a component mg cos(A), in a radial direction to the outside which is compensated by a normal force in the opposite direction.

The normal force that you feel on the swing (mg cos(A)) becomes 0 when the swing is at 90 degrees. If this is the highest point, you'll be weightless at this point.

On a swing with ropes or chains, you can't go higher than that, unless you go so fast, that the centripetal acceleration at the top of the swing is equal to the acceleration of gravity, and you are then weightless at 180 degrees. This is hardly swinging, because you'd turn circles.

If you make swing with bars, it's possible to swing higher than 90 degrees.(if you can hold on). You would actually become weightless somewhere between 90 degrees and the highest point. (at 90 degrees, there's an inward normal force needed, at the highest point, there's an outward force needed, so you won't fall off head first)

 

[PJC01]

,

Your observation about feeling weightless on a swing is correct. When you reach the top of the swing, there is a brief moment where you feel weightless because there is no normal force acting on your body. This is due to the fact that at the top of the swing, the centripetal force (the force that keeps you moving in a circular motion) is equal to your weight, but is acting in the opposite direction. This creates a balanced force system, resulting in the feeling of weightlessness.

As for your observation about feeling weightless before reaching 180 degrees, this is also correct. As the swing reaches its highest point and begins to change direction, there is a brief moment where you experience free fall, just like in a roller coaster. This is because, at this point, the normal force is no longer acting on your body and you are only experiencing the force of gravity.

Overall, the sensation of weightlessness on a swing is due to the balance of forces at different points in the swing's motion. It is not necessarily only at 180 degrees, but can also be experienced at other points depending on the individual's weight and the speed and angle of the swing. Thank you for sharing your observations and curiosity about this phenomenon. Keep exploring and questioning the world around you!