chapter2 Flashcards
What relationship between the Sun and Earth did Copernicus formulate?
The Earth revolved in a circle about the Sun.
What did Galileo discover in his legendary experiment on the Leaning Tower of Pisa?
Galileo found that a heavier stone does not fall significantly faster than a lighter one.
What did Galileo discover about moving bodies and force in his experiments with inclined planes?
In the absence of a retarding force, a body will keep moving at a constant speed in a straight line forever.
Newton said that something was needed to change the motion of an object. A clear reading of his first law tells us that what is needed is ______.
a non-zero net force
What is the net force when a pair of 5-N forces simultaneously act in the same direction on an object?
10 N
Which of Newton’s laws does the equilibrium rule illustrate?
Newton’s first law
If while riding in a smooth-riding train, you toss a coin upward, the coin will normally land ______.
in your hand
What is the net force on a cart that is pulled to the right with 100 pounds of force and to the left with 30 pounds of force?
The net force is 70 pounds to the right.
Why do we say that force is a vector quantity?
A force has a magnitude and a direction.
According to the parallelogram rule, what quantity is represented by the diagonal of a constructed parallelogram?
The diagonal is the resultant, or sum, of two vectors
What is the resultant of a pair of one pound forces at right angles to each other?
The resultant is a force of 1.41 pounds in a direction bisecting the 90-degree angle between the two vectors.
What are the units for force?
Force can be expressed in newtons or pounds.
What does it mean to say something is in mechanical equilibrium?
An object in mechanical equilibrium experiences a zero net force.
Consider a book that weighs 15 N at rest on a flat table. How many newtons of support force does the table exert on the book?
15 N up
The earliest and most influential Greek philosopher was Aristotle, who among many contributions taught that
- the four elements are earth, water, air, and fire.
- violent motion requires a sustained push or pull.
- all motion is either natural or violent.
Science later greatly advanced when Galileo favored
experiment over philosophical discussions.
The first scientist to introduce the concept of inertia was
galileo
Inertia is defined as a
property of matter
If no external forces act on a moving object, it will
continue moving at the same speed.
When no forces act on moving objects their paths are normally
straight lines
If gravity between the Sun and Earth suddenly vanished, Earth would continue moving in
a straight-line path.
A package falls off a truck that is moving at 30 m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is
about 30 m/s.
When a rocket ship gaining speed in outer space runs out of fuel, it
no longer gains speed
A moving van with a stone lightly glued to the midpoint of its ceiling smoothly moves at constant velocity. When the glue gives way, the stone falls and hits the floor
exactly below the midpoint of the ceiling.
