Physics problem: uniform circular motion 4. As for the light rod and light rope, one end of them is connected with a small ball, and the other end is pulled up by hand, so that they can make circular motion in the vertical plane A. It is impossible for a small ball connected by a rope to move in a circle at a uniform speed B. It is also impossible for a ball connected by a rod to move in a uniform circular motion C. The force of the rope on the ball must not work D. The force of the rod on the ball must not work The answer is: why is AC? How does light stick work on the ball? But isn't the supporting force component of the light bar the same as that of the light rope? Can you draw a picture?

Physics problem: uniform circular motion 4. As for the light rod and light rope, one end of them is connected with a small ball, and the other end is pulled up by hand, so that they can make circular motion in the vertical plane A. It is impossible for a small ball connected by a rope to move in a circle at a uniform speed B. It is also impossible for a ball connected by a rod to move in a uniform circular motion C. The force of the rope on the ball must not work D. The force of the rod on the ball must not work The answer is: why is AC? How does light stick work on the ball? But isn't the supporting force component of the light bar the same as that of the light rope? Can you draw a picture?

Because the light bar can provide support for the ball, it can ensure the ball to do uniform circular motion. If the ball does uniform circular motion in the vertical plane, the mechanical energy is not conserved. So the light bar does work on the ball. This is because the support force has a component in the direction of speed