Chapter 3 Flashcards
- What is the subject of the science of mechanics?
a. The proper description and the causes of motion of material objects
- Name the four basic kinds of motion according to Aristotle.
a. alteration – not motion at all (chemical change)
b. natural local motion – up or down motion
c. horizontal/violent motion – objects that are continually pushed or pulled; objects that are thrown (projectile)
d. celestial motion – motion of heavenly bodies; circular orbits
- Explain why only vertical motion was “natural motion” according to Aristotle.
a. because the objects do not need to be pushed or pulled
- According to Aristotle, why is the Earth “imperfect”?
a. because some of the prime substances were mixed together and not in their natural places
- What was the question Aristotle attempted to answer with his process known as antiperistasis?
a. “why does a projectile keep going after it had been thrown or struck?”
- How does Buridan’s example of a millwheel provide difficulty for the process of antiperistasis?
a. How could the air push on the back end of a millwheel when it has no end at all?
- Why did Aristotle believe a perfect vacuum couldn’t exist?
a. Because he correctly predicted that all objects will fall with the same speed in a vacuum but incorrectly predicted that this speed would be infinitely large. Infinite speed means that an object can be in two places at once because it would take no time at all to move from one place to another.
- What is the difference between uniform motion and uniformly accelerated motion?
- Give an example of an object with negative acceleration.
a. Uniform motion is motion at constant speed while uniformly accelerated motion is motion where the speed changes at constant or steady rate
a. Slowing down a car
- If the distance versus time graph is a straight line, what kind of motion does it indicate?
a. Uniform motion (constant speed)
- If the distance versus time graph is a curved line, what kind of motion does it indicate?
a. Uniformly accelerated motion
- Why did Galileo study “falling” by using pendulums and inclined planes?
a. He wants to determine how objects fall with no resistive effects and to slow down falling without changing the basic nature of the process
b. He wants to minimize the resistive effects of air, keeping the speed low.
- What kind of motion did Galileo determine that falling objects would have, ignoring resistive effects?
a. Uniformly accelerated motion
- How did Galileo rephrase Aristotle’s question about projectile motion?
a. Aristotle’s question: why do projectiles keep moving?
b. Galileo’s question: why do projectiles stop moving?
- Define inertia. With what characteristic of a body is inertia associated?
a. The property of body by which it keeps moving. Mass is a measure of inertia.
- Why did Galileo need the superposition principle in order to use pendulums and inclined planes to study falling objects?
a. Because pendulums and inclined planes both have horizontal and vertical motion. By the superposition principle, for objects with combined vertical and horizontal motions, the two motions can be analysed separately and then combined to yield the net result.
