Physics 100-Chapter 2 Flashcards

Questions and Answers

What class of motion, natural or violent, did Aristotle attribute to motion of the moon?

Natural

What state of motion did Aristotle attribute to the Earth?

Stationary/natural

What relationship between the Sun and the Earth did Copernicus formulate?

That the Earth circled the Sun

What did Galileo discover in his experiment on the Leaning Tower of Pisa?

That 2 objects of varying weights, when released at the same time, fell and hit the ground at the same time Signup and view all the answers

What did Galileo discover about moving bodies and force in experiments with inclined planes? (Select all that apply)

All of the above Signup and view all the answers

Is inertia the reason for moving objects maintaining motion?

False Signup and view all the answers

How does Newton's first law of motion relate to Galileo's concept of inertia?

Galileo stated that it was the tendency of things to resist changes in motion. Newton refined it by adding: 'Every object continues in a state of rest or uniform speed in a straight line unless acted on by a nonzero net force.' Signup and view all the answers

What type of path does a moving object follow in the absence of a force?

In the absence of force, a moving object moves along a straight line path indefinitely Signup and view all the answers

What is the net force on a cart that is pulled to the right with 100 lbs of force and to the left with 30 lbs of force?

70 pounds to the right Signup and view all the answers

Why is it said that force is a vector quantity?

Because it has both magnitude and direction Signup and view all the answers

According to the parallelogram rule, what quantity is represented by the diagonal of a constructed parallelogram?

The diagonal shows the resultant-the sum of two or more vectors Signup and view all the answers

What is the result of a pair of 1 lb forces at right angles to each other?

The resultant is √2 times (1.41) one of the vectors Signup and view all the answers

If the ropes were vertical, with no angle involved, what would be the tension in each rope?

The tension on each rope would be half her weight Signup and view all the answers

Can force be expressed in units of pounds and also in units of newtons?

True Signup and view all the answers

What is the net force on an object that is pulled with forces of 80 newtons to the right and 80 newtons to the left?

The net force is zero newtons Signup and view all the answers

What is the net force on a bag pulled down by gravity with a force of 18 newtons and pulled upward by a rope with a force of 18 newtons?

The net force is zero newtons Signup and view all the answers

What does it mean to say that something is in mechanical equilibrium?

When the net force on something is zero Signup and view all the answers

What is the equilibrium rule for forces in symbolic notation?

ƩF= 0 Signup and view all the answers

A book weighs 15 newtons at rest on a flat table. How many newtons of support force does the table provide? What is the net force on the book in this case?

The number of newtons of support force must equal the weight of the book=15 newtons. The net force on the book is zero Signup and view all the answers

When you stand at rest on a bathroom scale, how does your weight compare with the support force by the scale?

Your weight is the force you exert on a supporting surface, which when in equilibrium is the gravitational force on you. The scale reading shows both your weight and the support force Signup and view all the answers

A bowling ball at rest is in equilibrium. Is the ball in equilibrium when it moves at constant speed in a straight-line path?

True Signup and view all the answers

What is the net force on an object in either static or dynamic equilibrium?

Static equilibrium-all acting forces always balance to zero. Dynamic equilibrium-all acting forces balance to zero Signup and view all the answers

If you push on a crate with a force of 100 newtons and it slides at constant velocity, how great is the friction acting on the crate?

The friction is 100 newtons Signup and view all the answers

What concept was not understood in the 16th century when people couldn't conceive of a moving Earth?

The concept of inertia Signup and view all the answers

A bird sitting in a tree is traveling at 30 km/s relative to the faraway Sun. When the bird drops to the ground below, does it still move at 30 km/s, or does this speed become zero?

It moves at 30 km/s relative to the Sun Signup and view all the answers

Stand next to a wall that travels at 30 km/s relative to the Sun. With your feet on the ground, you also travel at the same 30 km/s. Do you maintain this speed when your feet leave the ground? What concept supports the answer?

Yes, you maintain the same speed. Inertia Signup and view all the answers

What is inertia?

Property of things to resist changes in motion Signup and view all the answers

What is Newton's First Law of Motion?

Aka: The law of inertia. Every object continues in a state of rest or uniform speed in a straight line unless acted upon by a nonzero net force Signup and view all the answers

What is force?

A push or a pull Signup and view all the answers

What is net force?

Vector sum of forces that act on an object Signup and view all the answers

What is a vector?

An arrow, drawn to scale, used to represent a vector quantity Signup and view all the answers

What is a vector quantity?

A quantity that has both magnitude and direction. EX: force Signup and view all the answers

What is a scalar quantity?

A quantity that has magnitude but not direction. EX: mass and volume Signup and view all the answers

What is resultant?

Net result of a combination of two or more vectors Signup and view all the answers

What is mechanical equilibrium?

State of an object or system of objects for which there are no changes in motion. If an object is at rest, the state of rest persists (Newton's 1st law). If an object is moving, its motion continues w/o change Signup and view all the answers

What is the equilibrium rule?

For any object or system of objects in equilibrium, the sum of the forces acting equals zero. Equation: ƩF= 0 Signup and view all the answers

Study Notes

Aristotle's Concepts

Attributed the moon's motion to natural motion.
Considered the Earth to be stationary and in a natural state.

Copernicus's Model

Proposed that the Earth orbits the Sun, challenging previous geocentric views.

Galileo's Experiments

Demonstrated that two objects, regardless of weight, fall at the same rate using the Leaning Tower of Pisa.
Found that on an inclined plane, objects increase speed going down and decrease speed going up. A horizontal object in a vacuum moves indefinitely without forces.

Inertia and Motion

Inertia refers to the property that objects resist changes in motion.
Newton's First Law of Motion builds on Galileo's concepts, stating objects remain at rest or in uniform motion unless affected by a net force.

Forces and Equilibrium

A moving object follows a straight line indefinitely if no force acts upon it.
Introduced the concept of net force: the difference between opposing forces; ex: 100 lbs. right and 30 lbs. left results in a net force of 70 lbs. to the right.
Described forces as vector quantities, with both magnitude and direction.

Resultant Forces

The parallelogram rule explains that the diagonal of a constructed parallelogram represents the resultant of vector quantities.
A combination of two 1 lb. forces at right angles results in a resultant of approximately 1.41 lbs.

Mechanical Equilibrium

Mechanical equilibrium occurs when net forces acting on an object equal zero.
For a book resting on a table, the support force equals its weight (15 newtons), resulting in a net force of zero.
A bowling ball at rest and one in constant straight-line motion are both in equilibrium.

Friction and Forces

When a force of 100 newtons moves an object at constant velocity, friction equals 100 newtons.

Concepts of Inertia

Inertia explains why a bird retains its speed relative to the Sun when it drops from a tree, maintaining 30 km/s.
Individuals maintain the same speed when leaving the ground due to inertia.

Definitions of Key Terms

Force: A push or pull acting on an object.
Net Force: The vector sum of all forces acting on an object.
Vector: Representation of a vector quantity, illustrated as an arrow.
Vector Quantity: Quantities possessing both magnitude and direction, such as force.
Scalar Quantity: Quantities defined only by magnitude, like mass and volume.
Resultant: The combined effect of two or more vectors.
Mechanical Equilibrium: A state where objects do not change motion; persistence in rest or steady motion.
Equilibrium Rule: Equation stating that forces in equilibrium sum to zero (ƩF = 0).

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Description

Test your knowledge of key concepts from Chapter 2 of Physics 100. This quiz covers the motion theories of Aristotle and significant developments by Copernicus and Galileo. Brush up on important definitions and relationships in motion.