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Vertical Forces & Acceleration quiz #1

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  • What best describes the normal force acting on a book that is sitting on a desk?
    The normal force is an upward contact force exerted by the desk on the book, balancing the downward gravitational force (weight) of the book. If the book is at rest and in equilibrium, the normal force equals the magnitude of the book's weight.
  • Why is the support force on an object often called the normal force?
    The support force is called the normal force because it acts perpendicular (normal) to the surface of contact, providing the upward force that balances the object's weight when at rest on a surface.
  • In which direction does the normal force (Fn) act on an object resting on a surface?
    The normal force (Fn) acts perpendicular and away from the surface, typically upward, opposing the downward force of gravity.
  • How is the normal force exerted on a rider at a specific point determined in vertical force problems?
    The normal force on a rider at a specific point is found by analyzing all vertical forces acting on the rider, including gravity and any acceleration. If the rider is in equilibrium, the normal force equals the rider's weight. If the rider is accelerating vertically, the normal force is calculated using Newton's second law: Fn = mg + ma, where a is the vertical acceleration at that point.
  • What is the direction of the weight force acting on an object near Earth's surface?
    The weight force always points toward the center of the Earth, which is typically downward. This direction remains unless otherwise specified in a problem.
  • How does the value of gravitational acceleration (g) change when moving from Earth to the Moon?
    The value of g decreases when moving from Earth to the Moon, dropping from 9.8 m/s^2 on Earth to 1.62 m/s^2 on the Moon. This change affects the weight of objects but not their mass.
  • If a scale shows your 'weight' as 70 kilograms, what physical quantity is it actually measuring?
    The scale is actually measuring your mass, not your weight. Mass is given in kilograms and does not change with location.
  • What happens to the acceleration of an object if the only force acting on it is gravity?
    The object will accelerate downward with an acceleration equal to g, which is 9.8 m/s^2 near Earth's surface. This is known as free fall.
  • In a vertical force problem, what does a positive acceleration indicate about the direction of motion?
    A positive acceleration indicates that the object is accelerating upward. This occurs when the upward force exceeds the downward force.
  • What is the net force on an object if the upward and downward forces are equal in magnitude?
    The net force is zero if the upward and downward forces are equal. This means the object is in equilibrium and has no acceleration.