Happy New Year, all, and welcome back to the physics demo highlight of the week! This week we’re taking a look at a classic kinematics demonstration, the funnel cart. It’s presented in this new video starring Ruhi Perez.

 

 

When we push the cart forward, both the ball and the cart are traveling horizontally with the same velocity. When the ball is launched, it has a new motion and velocity in the vertical direction. Even though the ball now has a second, vertical motion, its horizontal motion will not change. Thus, the ball and the cart travel the same horizontal distance in the same amount of time, and the ball lands in the cart! Since the funnel catches the ball, we can clearly see that this demo shows the independence of motion. It is interesting to note that to you and me, it appears that the ball traveled in a parabola or an arch. If you were sitting in the funnel and looking up at the ball, moving with the cart, it would appear that the ball only traveled directly up and then directly back down again! This is an example of examining a physical phenomenon in different reference frames.

For added challenge, consider: What would happen if the track were placed on a slope? Or if the cart had an engine that made it speed up over time? Or if we hung a weight on a string off the end to drag the cart fowards, or to slow it down?