To investigate Newton's First and Second Laws by studying the motion of a small sphere.
Newton's First Law tells what happens to an object when no unbalanced forces act on it, and Newton's Second Law tells what happens to an object when an unbalanced force does act on it. In this simple activity, you will observe what happens to a small sphere when forces are applied, as well as when no force is applied at all. Of course, the situation in which no forces act can only be approximated here - there is a small friction force that the table exerts on the ball - but try to extrapolate your observations to the situation where no friction acts. (In plain English: "Try to ignore friction.") In other words, try to be clear about whether the motion of the ball is due to no forces acting, or due to the friction force.
assorted small spheres
What happens to the motion of an object when no unbalanced forces
act on it? A smooth sphere rolling across a smooth, level tabletop
almost meets the requirements of Newton's First Law. The earth pulls
downward on it (its weight) and the table pushes upward on it, but
these 2 forces balance (cancel each other out). There is a small
friction force acting to slow the ball down, but this friction force
is very small (Try to ignore it.). Therefore, the sphere moves almost
as if no forces act on it. Investigate the motion of a rolling sphere
until you can answer the following questions.
Hint: Do not try to answer these questions in the space provided on this sheet. Invest in a sheet of paper, please.
can apply a relatively constant force to a sphere by blowing on it
through a straw. Newton's Second Law describes what happens to a
motion if an unbalanced force acts on it.