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?
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What did Galileo discover about moving bodies and force in experiments with inclined planes? (Select all that apply)
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Is inertia the reason for moving objects maintaining motion?
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How does Newton's first law of motion relate to Galileo's concept of inertia?
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What type of path does a moving object follow in the absence of a force?
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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?
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Why is it said that force is a vector quantity?
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According to the parallelogram rule, what quantity is represented by the diagonal of a constructed parallelogram?
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What is the result of a pair of 1 lb forces at right angles to each other?
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If the ropes were vertical, with no angle involved, what would be the tension in each rope?
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Can force be expressed in units of pounds and also in units of newtons?
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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?
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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?
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What does it mean to say that something is in mechanical equilibrium?
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What is the equilibrium rule for forces in symbolic notation?
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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?
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When you stand at rest on a bathroom scale, how does your weight compare with the support force by the scale?
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A bowling ball at rest is in equilibrium. Is the ball in equilibrium when it moves at constant speed in a straight-line path?
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What is the net force on an object in either static or dynamic equilibrium?
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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?
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What concept was not understood in the 16th century when people couldn't conceive of a moving Earth?
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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?
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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?
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What is inertia?
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What is Newton's First Law of Motion?
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What is force?
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What is net force?
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What is a vector?
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What is a vector quantity?
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What is a scalar quantity?
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What is resultant?
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What is mechanical equilibrium?
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What is the equilibrium rule?
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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.