Scalars and Vectors Quiz
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Questions and Answers

Which of the following is a scalar quantity?

  • Weight
  • Velocity
  • Displacement
  • Time (correct)

    • The net force is the sum of all forces acting on an object.

    True (A)

    What is the state of an object when the net force acting on it is zero?

    equilibrium

    Newton's First Law of Motion is also known as the Law of ______.

    <p>inertia</p> Signup and view all the answers

    According to Newton's Second Law of Motion, what is the relationship between force, mass, and acceleration?

    <p>Force = mass * acceleration (B)</p> Signup and view all the answers

    The normal force always acts parallel to the surface of contact.

    <p>False (B)</p> Signup and view all the answers

    What causes our sense of weight?

    <p>normal force</p> Signup and view all the answers

    Match the following laws with their descriptions:

    <p>Law of Inertia = An object in motion stays in motion unless acted upon by an external force. Law of Action and Reaction = For every action, there is an equal and opposite reaction. F = ma = The net force acting on an object is equal to the mass of the object multiplied by its acceleration.</p> Signup and view all the answers

    What unit is used to measure gravitational field strength?

    <p>Newtons per kilogram (N/kg) (C)</p> Signup and view all the answers

    Everything with mass has its own gravitational field.

    <p>True (A)</p> Signup and view all the answers

    What happens to the gravitational field strength if you double the distance from an object?

    <p>It decreases by a factor of four</p> Signup and view all the answers

    The force exerted on an object due to gravity is called ______.

    <p>weight</p> Signup and view all the answers

    What happens to your apparent weight when an elevator accelerates upwards?

    <p>You feel heavier. (D)</p> Signup and view all the answers

    The normal force always equals the actual weight of an object.

    <p>False (B)</p> Signup and view all the answers

    What two things determine the acceleration of an object?

    <p>Net force and mass</p> Signup and view all the answers

    In a force diagram, the ______ force acts upwards and is equal to the weight force.

    <p>normal</p> Signup and view all the answers

    What is the net force on an object in equilibrium?

    <p>Zero (D)</p> Signup and view all the answers

    Flashcards

    Scalar

    A quantity with only magnitude, like time or mass.

    Vector

    A quantity with both magnitude and direction, such as velocity.

    Resultant Vector

    The combined effect of two or more vectors.

    Equilibrium

    State when net force on an object is zero.

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    Newton's First Law

    An object remains at rest or in uniform motion unless acted on by an unbalanced force.

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    Normal Force

    Force exerted by a surface perpendicular to the object in contact.

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    Gravitational Field

    An invisible field created by mass that extends into space.

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    Net Force

    The sum of all forces acting on an object.

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    Gravitational Field Strength (g)

    The force experienced per kilogram due to gravity.

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    Gravitational Field Strength Formula

    g = GM/r², where G is gravitational constant, M is mass, r is distance.

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    Inverse Square Relationship

    Gravitational strength decreases with the square of distance.

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    Weight

    Force exerted on an object due to gravity, calculated as mass times acceleration due to gravity.

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    Driving Force

    A force that pushes or propels an object forward.

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    Frictional Force

    Resistive force opposing motion between two surfaces.

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    Force Diagrams

    Visual representations showing all forces acting on an object.

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    Apparent Weight

    Force exerted by an object on a surface, can differ from actual weight.

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    Study Notes

    Scalars and Vectors

    • Scalars: Quantities with only magnitude (size).
      • Examples: time, mass, distance, speed.
    • Vectors: Quantities with both magnitude and direction.
      • Examples: weight, displacement, velocity.

    Adding Vectors in Two Dimensions

    • Vectors can be broken down into their horizontal and vertical components using trigonometry.
    • Adding Vectors: To add vectors, add their horizontal and vertical components separately to find the net vector.
    • Resultant Vector: The combination of two or more vectors is called the resultant vector.
    • Net Force: The sum of all forces acting on an object.
    • Equilibrium: When the net force on an object is zero, the object is in equilibrium (at rest or moving at a constant velocity).

    Vectors

    • In diagrams, vectors can be visualized as arrows, with length representing magnitude and direction representing the direction of the force.
    • Vectors can be broken down into horizontal and vertical components.
    • To find the net direction of a box subjected to multiple forces, visualize the horizontal and vertical components of each force and their sum.

    Newton's Laws

    • First Law of Motion (Law of Inertia): An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
    • Second Law of Motion: The net force acting on an object is equal to the mass of the object multiplied by its acceleration (F = ma).
      • This means that a larger force is required to accelerate a heavier object.
      • An accelerated object applies a force equal to its mass times acceleration.
    • Third Law of Motion (Law of Action and Reaction): For every action, there is an equal and opposite reaction.
      • When you push on an object, the object pushes back on you with the same force.
      • This explains why hitting a tennis ball with force causes a reaction force that can lead to wrist injuries.

    Normal Force

    • The normal force is the force exerted by a surface on an object in contact with it.
    • It acts perpendicular to the surface.
    • It is equal in magnitude and opposite in direction to the force exerted by the object on the surface.
    • This force is responsible for our sense of weight.
    • When in freefall, we don't feel our weight because there's no normal force acting on us.

    Gravity and Gravitational Fields

    • Gravitational Fields: An invisible field created by objects with mass that extends outward into space.
      • Everything with mass has its own gravitational field.
      • We only experience the fields of objects with significant mass, such as planets.
    • Gravitational Field Strength (g): Measured in Newtons per kilogram (N/kg) or meters per square second (m/s²).
    • Gravitational Field Strength Formula: g = GM/r² where G is the gravitational constant (6.67 x 10⁻¹¹), M is the mass of the object, and r is the distance from the center of mass to the point where the field is being measured.
    • Inverse Square Relationship: Gravitational field strength is inversely proportional to the square of the distance from the center of the object.
      • If you double the distance, the gravitational field strength decreases by a factor of four.
    • Weight: The force exerted on an object due to gravity.
      • Calculated by multiplying mass by acceleration due to gravity.
    • Weight in an Elevator: When an elevator accelerates upward, you feel heavier because the normal force increases, adding to your weight. When it accelerates downward, you feel lighter because the normal force decreases.

    Driving Force and Frictional Force

    • Driving Force: A force that pushes or propels an object.
    • Frictional Force: Resistive force that opposes motion caused by the interaction between two surfaces in contact.
    • Net Force: The sum of all forces acting on an object.
      • Determines the acceleration of the object.
      • If a driving force acts on a box against a frictional force, the net force is calculated by subtracting the frictional force from the driving force.
      • This net force determines the direction and magnitude of the box's movement.

    Forces

    • Forces are vectors, which means they have magnitude and direction.
    • Net force is the sum of all forces acting on an object.
    • The acceleration of an object is directly proportional to the net force and inversely proportional to its mass.
    • Friction opposes the movement of an object.
    • In equilibrium, the net force on an object is zero.
    • When a force is applied to an object that doesn’t move, the frictional force is equal and opposite to the applied force.
    • If the applied force exceeds the frictional force, the object will move.

    Force Diagrams

    • Force diagrams are visual representations of the forces acting on an object.
    • The weight force (or gravitational force) acts downwards from the center of mass of an object.
    • The normal force acts upwards and is equal to the weight force.
    • The normal force is often denoted as Fn or N.

    Apparent Weight and Normal Forces

    • The apparent weight of an object is the force it exerts on a supporting surface.
    • The normal force is equal to the apparent weight.
    • The apparent weight can be different from the actual weight of an object, especially when the object is accelerating or when the forces are not evenly distributed.
    • For example, when a person is lying on a bed, the apparent weight is not evenly distributed between their legs because their center of mass is not located at the midpoint of their body.
    • The force exerted on each leg is proportional to the distance from the leg to the center of mass.

    Gravitational Fields

    • The strength of a gravitational field is inversely proportional to the square of the distance from the source of the field.
    • The gravitational field strength is a vector quantity, meaning it has both magnitude and direction.
    • Two objects with different masses will have different gravitational field strengths at a given distance.
    • The gravitational field strength can be calculated using the formula: g = Gm/r2, where g is the gravitational field strength, G is the gravitational constant, m is the mass of the object, and r is the distance from the object.
    • The point where the gravitational fields of two objects cancel each other out is called the point of zero net force.
    • The point of zero net force is closer to the object with the smaller mass because its field strength falls off more rapidly with distance.

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    Test your understanding of scalars and vectors, including their definitions, examples, and how to add vectors in two dimensions. Explore concepts such as resultant vectors, net force, and equilibrium to solidify your grasp of these fundamental physics topics.

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