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Physics: Newtonian Mechanics and Forces

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이 집합의 용어 (20)

  • Why do all objects fall at the same rate in a vacuum?
    Because the ratio of gravitational force (weight) to mass is the same for every object, equal to \(g\), resulting in identical acceleration.
  • What does the equation Weight = mg imply about acceleration in free fall?
    Weight divided by mass equals \(g\), so acceleration due to gravity is constant for all masses.
  • Why do objects of different mass slide down a frictionless incline together?
    Because both the gravitational component along the slope and inertia scale with mass, which cancel out, making acceleration depend only on the incline angle.
  • How does air resistance affect a ball thrown upward and caught at the same height?
    Air resistance opposes motion both ways, so the ball returns slower than it was thrown due to energy loss.
  • What force does a bathroom scale read when you stand still on it?
    The upward support (normal) force balancing gravity, equal in magnitude to your weight at equilibrium.
  • Are weight and mass the same physical quantity?
    No, weight is a force measured in Newtons, while mass is the amount of matter; they are related but distinct.
  • When do action and reaction forces occur relative to each other?
    They occur simultaneously at the exact same time, with no delay.
  • How does the normal force compare to weight on a horizontal surface?
    On a flat horizontal surface, the normal force equals the full weight of the object.
  • How does the normal force compare to weight on an inclined surface?
    The normal force equals weight times \(\cos(\theta)\), which is less than the full weight.
  • What does Newton's Third Law say about the magnitude of action and reaction forces?
    They are always exactly equal in magnitude and opposite in direction.
  • Why can't a boxer punch tissue paper with more than 50 N of force if the paper can only push back with 50 N?
    Because Newton's Third Law requires equal and opposite forces; the weaker object limits the maximum force.
  • What is the reaction force to Earth's gravity pulling a ball downward?
    The ball's gravity pulling Earth upward with equal magnitude and opposite direction.
  • Is air resistance the reaction force to gravity on a falling ball?
    No, air resistance is a separate force from the interaction between the ball and air, not paired with gravity.
  • When a bat hits a ball, when does the ball push back on the bat?
    At the exact same instant the bat pushes the ball; the forces are simultaneous.
  • Why don't action-reaction forces cancel each other out?
    Because they act on different objects, so they cannot cancel.
  • What two forces act on you when standing still on a bathroom scale?
    Gravity pulling you down and the scale's support force pushing you up, equal and opposite.
  • If an elevator accelerates upward, how does the scale reading change?
    The scale reads more than normal because it must provide extra upward force to accelerate you.
  • Why doesn't a heavier block slide faster on a frictionless incline?
    Because increased gravitational force is balanced by increased inertia; acceleration is independent of mass.
  • What determines the maximum force in an interaction like a punch?
    The weaker object limits the maximum force because it can only push back with a certain force.
  • How does the normal force change as the incline angle increases?
    The normal force decreases because it equals weight times \(\cos(\theta)\), which gets smaller as the angle increases.