Give Now

A Moment of Science

Take The A Moment Of Science Physics Quiz!

This is just a little physics quiz to get you thinking!

Curved metal pipe

Photo: timrb (Flickr)

Will a metal tube change the direction of the golf ball?

The A Moment of Science physics quiz…

Begin The Quiz…

You have a long metal tube that is curved. You also have a miniature golf ball that you are knocking into one end and out the other.

How does the ball move after it leaves the other end of the tube? Does it move in a straight line or a curve? Perhaps it starts by moving in a curved line, then gradually straightens out? Or something else?

Curved Or Straight?

When this question was given informally to a group of undergraduate students, about half of them suspected some kind of curved motion would remain in the ball after it leaves the tube. This, however, is incorrect.

Once the ball leaves the tube it will move in a perfectly straight line. What’s interesting, though, is that it wasn’t until the 17th century that this was realized to be the case.

Curved Tube, Curved Motion

For hundreds of years people thought that some aspect of the thing that moved an object stayed in the object. That sounds a little weird, but if you thought the ball would continue in a curved path, you were subscribing to this theory. Curved tube, curved motion.

Newton’s Laws

Newton’s laws of motion stated that an object will always move in a straight line unless it is prevented from doing so. The curved tube prevents the ball from moving straight only as long as the ball is inside. Once free, however, it moves straight once again. And it will continue to do so as long as nothing interrupts this motion.

  • Anonymous

    I question this! It would be the case if the tube were frictionless. However, in other circumstances (all!) then would the ball not receive some spin when it hits the wall within the tube(I assume that there is some clearance between the ball and the tube). When the ball leaves the tube it will, like a top, carry some spin with it, so will not proceed in a straight line.

Stay Connected

What is RSS? RSS makes it possible to subscribe to a website's updates instead of visiting it by delivering new posts to your RSS reader automatically. Choose to receive some or all of the updates from A Moment of Science:

Support for Indiana Public Media Comes From

About A Moment of Science

Search A Moment of Science