David and Alan hit a ball so that it travels in a circle: Observational Experiment

Aim

To find a pattern in the direction of the vector sum of the forces exerted by other objects on an object moving in a circle at constant speed.

Prior Knowledge

• Newton's Laws. Drawing free-body diagrams.

Description of the Experiment

In the first video David hits a ball with a mallet so that it travels in a circle. Observe how he is hitting the ball.

In the second video, Alan hits a ball with a stick so that it travels in a circle. Observe how he is hitting the ball.

Youtube movies can be stepped frame by frame using the , and . keys on your keyboard. If you want to download the movie to your computer, right-click or control-click HERE.

Youtube movies can be stepped frame by frame using the , and . keys on your keyboard. If you want to download the movie to your computer, right-click or control-click HERE.

Questions

• How is David hitting the ball (direction)? How is Alan hitting the ball?



• What are the objects that interact with the ball in each of the experiments? Draw a force (free-body) diagram for the ball at any point of its path for both experiments.



• When an object moves in a circle, is its velocity changing? Assume that the speed of the bowling ball remains almost constant and find the direction of the acceleration of the ball assuming that the direction of the acceleration is the same as the direction of the velocity change vector.



• Choose three positions on the ball's path and repeat a force (free-body diagram) for the ball. Do you see a pattern in the direction of the sum of the forces exerted on the ball?