Question

MOTION OF A BALL roll a ball along the floor so that it moves at a reasonable speed. Walk beside it and place packets to mark the locations of the ball every second. Make sure to roll the tennis ball carefully so that it rolls in as straight a line as you can manage. If the ball starts to curl near the end of its motion, what will you do to deal with the situation?

a) Do you think that if you repeat the experiment you would get the same results? Is it worth repeating the experiment again? Explain.

b) How would you classify the object’s motion: motion with constant rate, increasing rate/decreasing rate? Explain how you decided.

c) Now imagine that you want to describe the experiment to Saalih, so Saalih can understand both the procedure and the results. Is it better to use words or there is another, more concise way? Think about which parts of the experiment and the results are important and which are not. Once you have thought about this, describe the outcome of the experiment to Saalih in an efficient way.

Answer 1

a) If we repeat the experiment the results are not exactly same but closer. It is worth repeating to have better understanding of the process what is happening.

b) The motion is decreasing, for every one second the distance roleld by the ball is lesser than the previous one.

c) As the ball rolls down the floor the motion is decelerating and finally the ball stops as the ball slows down.

The reason for slowing down the ball.

As the ball rolls down the bottom surface is slight deformed and the point of contact with the floor is not a single point but an area of contact. The front part of the contact are pushes the floor with more force than the back part. As a result the normal force is not at the center of the contact area but shifted towards the front and as a result there is an anti clockwise torque on the ball and causes angular deceleration.