Forces and Interactions flashcards

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What is a force?Forces and Free-Body Diagrams: A vector interaction that can change motion or shape.
What is the SI force unit?Forces and Free-Body Diagrams: The newton (N).
What is a contact force?Forces and Free-Body Diagrams: A force involving physical contact between objects.
Can an object move with zero net force?Forces and Free-Body Diagrams: Yes, at constant velocity in an inertial frame.
What is a free-body diagram?Forces and Free-Body Diagrams: A diagram of external forces on one selected object.
What is a normal force?Forces and Free-Body Diagrams: A support force perpendicular to a contacting surface.
Should forces exerted by the object appear on its diagram?Forces and Free-Body Diagrams: No; show forces acting on it.
Is velocity a force?Forces and Free-Body Diagrams: No; it describes motion, not an interaction.
What is net force?Forces and Free-Body Diagrams: The vector sum of external forces on one object.
What is the symbol ΣF?Forces and Free-Body Diagrams: The sum of forces acting on the chosen object.
What does zero net force imply?Forces and Free-Body Diagrams: Zero acceleration in an inertial frame.
Can forces on different objects cancel in one sum?Forces and Free-Body Diagrams: No; a free-body sum concerns one target.
What is inertia?Newton’s First and Second Laws: Resistance to a change in velocity.
What does the first law predict at zero net force?Newton’s First and Second Laws: Constant velocity, including rest.
What is an inertial frame?Newton’s First and Second Laws: A frame where Newton’s first law holds in its usual form.
Does constant velocity mean no individual forces?Newton’s First and Second Laws: No; forces may balance.
What is Newton’s second law for constant mass?Newton’s First and Second Laws: ΣF = ma.
What direction is acceleration?Newton’s First and Second Laws: The direction of net force.
What is 1 N in base units?Newton’s First and Second Laws: 1 kg·m/s².
What happens to a at fixed F if m doubles?Newton’s First and Second Laws: Acceleration halves.
How do you find net force on a line?Newton’s First and Second Laws: Add signed force components on one object.
What is the acceleration formula?Newton’s First and Second Laws: a = ΣF/m.
Why separate applied and net force?Newton’s First and Second Laws: Other forces can oppose or add to the applied force.
Can vertical forces balance while horizontal forces do not?Newton’s First and Second Laws: Yes.
What is a third-law pair?Newton’s Third Law: Equal and opposite forces one object exerts on another and vice versa.
Where do third-law forces act?Newton’s Third Law: On two different objects.
Do third-law forces cancel on one free-body diagram?Newton’s Third Law: No.
Are weight and normal on one book a third-law pair?Newton’s Third Law: No; both act on the book.
What pushes a walker forward?Newton’s Third Law: A forward static-friction force from the ground.
What gives a driven tire forward traction?Newton’s Third Law: The road’s static-friction force on the tire.
Does a rocket need surrounding air for thrust?Newton’s Third Law: No; it interacts with expelled exhaust.
Can friction point in the direction of motion?Newton’s Third Law: Yes, static friction can propel a walker or tire.
What do balanced forces have in common?Newton’s Third Law: They act on the same object and sum to zero.
What identifies a third-law pair?Newton’s Third Law: The same two objects exert forces on each other.
What pairs with table-on-book?Newton’s Third Law: Book-on-table.
What pairs with Earth-on-book?Newton’s Third Law: Book-on-Earth.
What is mass?Gravity, Mass, and Weight: A measure of inertia, expressed in kilograms.
What is weight?Gravity, Mass, and Weight: The gravitational force on an object.
What is the weight equation?Gravity, Mass, and Weight: W = mg under a local g model.
What unit measures weight?Gravity, Mass, and Weight: Newton (N).
What is Newtonian gravitational attraction?Gravity, Mass, and Weight: A mutual attractive force between masses.
What does inverse-square mean?Gravity, Mass, and Weight: Force scales as one divided by separation squared.
What happens if r doubles?Gravity, Mass, and Weight: Force becomes one quarter under the model.
Why use nearly constant g near the surface?Gravity, Mass, and Weight: Small heights barely change distance from Earth’s center.
What is air resistance?Gravity, Mass, and Weight: A force from movement relative to air.
What is terminal speed?Gravity, Mass, and Weight: An approximately steady falling speed when drag balances weight.
Is gravity present in orbit?Gravity, Mass, and Weight: Yes; it helps curve the path.
What does apparent weightlessness often mean?Gravity, Mass, and Weight: Little or no support force during free fall.
What is static friction?Friction and Motion in Context: Friction at a contact without relative sliding.
What is kinetic friction?Friction and Motion in Context: Friction while surfaces slide relative to each other.
What direction does friction oppose?Friction and Motion in Context: Relative motion or its tendency at the contact.
Can static friction propel motion?Friction and Motion in Context: Yes, as with walking or driven tires.
What is deceleration in a chosen direction?Friction and Motion in Context: Acceleration opposite the current velocity, reducing speed.
What is braking distance?Friction and Motion in Context: Distance traveled while braking to a stop.
What is reaction distance?Friction and Motion in Context: Distance traveled before a response or braking begins.
At fixed deceleration, how does braking distance scale with speed?Friction and Motion in Context: With the square of initial speed.
What is an incline?Friction and Motion in Context: A surface tilted relative to horizontal.
What is the downhill weight component?Friction and Motion in Context: mg sinθ for an incline angle θ above horizontal.
What is the perpendicular weight component?Friction and Motion in Context: mg cosθ toward the surface.
Does friction always point uphill on a ramp?Friction and Motion in Context: No; it opposes relative sliding or its tendency.