PHYS 1405 – Conceptual Physics I
Introduction to Inertia
Note: The following activity makes use of a bowling ball. If lifting and handling a bowling ball is physically difficult for you please substitute a croquet ball.
1. Set a bowling ball on the floor at rest. Describe its motion.
2. What do you have to do to get the bowling ball to start moving?
3. Carry out your answer to question 2 and describe the subsequent motion.
4. Do you need to push on the bowling ball to keep it moving once you’ve started?
5. Why might the bowling ball eventually stop?
6. Do you think the bowling ball would stop sooner if you had rolled it on carpet? Explain.
7. What do you have to do to stop the bowling ball?
Mass is a measure of the total amount of material in an object. Weight is defined as the force of gravity due to Earth on object’s mass.
8. What direction does the force of gravity point?
9. Carefully lift the bowling ball straight up. Are you feeling the ball’s weight or its mass? Explain.
10. Carefully, shake the bowling ball back and forth horizontally. Are you feeling the ball’s weight or mass? Explain.
11. Why do you think a bowling ball was chosen for this activity as opposed to something like a golf ball?
12. Summarize your observations by completing the following.
a) If a massive object is at rest it will _____________
b) If a massive object is moving it will _____________
c) To start a massive object moving you must __________________
d) To stop a massive object moving you must __________________
e) The more mass an object has the (circle one) greater/less effort is required to change its motion.
Galileo was the first person to identify the property of
matter that it tends to resist a change in motion. He coined the term inertia to describe this property, from the Latin for lazy.
A massive object at rest will remain at rest and a massive object moving at a constant speed in a straight line will continue to do so unless acted on by a net external force.