Thank you for the opportunity to help you with your question!

Length=0.7m

revolutions=7.9/sec

The period of a ball in circular motion is 1/Frequency so 1/7.9=0.1266 seconds

The speed is distance over time and the distance traveled in 1 second is:

u multiply the number of revolutions per second with the circumference of the circle to find speed (m/s)* circumfrenc2(0.7m)(3.14)e of circle = (2r)(pi)

=4.396m

speed of the ball: 4,396 * 7.9 =34.7284m/s

Please let me know if you need any clarification. I'm always happy to answer your questions.