Physics Chapter on Forces and Motion
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Questions and Answers

What must be true for an object to remain stationary and in equilibrium?

  • The object must always have a net force acting on it.
  • The forces acting on the object must be greater than the mass.
  • The object must be moving at a constant speed.
  • The resultant force acting on it must be zero. (correct)

    • The horizontal component of the tension in cable X is negative when the pot is stationary.

    True

    What is the resultant force in the y-direction when the vertical forces sum to 2.24 N?

    2.24 N up

    The resultant force acting on an object in equilibrium must equal _____.

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

    Calculate the resultant horizontal force based on the forces given: 6N at 40° and 8N at 25°.

    <p>-2.65 N to the left</p> Signup and view all the answers

    Match the force components with their calculated value:

    <p>Horizontal Component (Fx) = -2.65 N Vertical Component (Fy) = 2.24 N Resultant Force (FR) = 3.47 N Angle (θ) = 40.2°</p> Signup and view all the answers

    What is the angle θ when the vertical resultant is 2.24 N and horizontal resultant is -2.65 N?

    <p>40.2°</p> Signup and view all the answers

    What is the overall resultant force when the net vertical and net horizontal forces are combined?

    <p>3.47 N</p> Signup and view all the answers

    What is the result of applying a downward force while pushing an object?

    <p>The total downward force increases.</p> Signup and view all the answers

    When pulling an object, the normal force is always less than the gravitational force.

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

    What is the vertical component of a 55 N force acting at an angle of 60°?

    <p>27.5 N</p> Signup and view all the answers

    The opposite of adding two forces is ________ a force into its components.

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

    Match the forces with their correct components:

    <p>R = 55 N, θ = 60° = R sin(60°) = 47.4 N (vertical), R cos(60°) = 27.5 N (horizontal) R = 0.75 N, θ = 40° = R sin(40°) = 0.48 N (vertical), R cos(40°) = 0.57 N (horizontal) R = 200 N, θ = 25° = R sin(25°) = 84.9 N (vertical), R cos(25°) = 180.3 N (horizontal)</p> Signup and view all the answers

    When two children pull a go-kart, and one exerts a 30 N force, what is a possible value for the component of this force that is acting forwards, if it makes a 30° angle with the horizontal?

    <p>25.98 N</p> Signup and view all the answers

    Calculate the weight of an 8 kg flower pot.

    <p>78.4 N</p> Signup and view all the answers

    What is the maximum force of static friction when the coefficient of static friction is 0.75 and the mass of the object is 700 kg?

    <p>5145 N</p> Signup and view all the answers

    The applied force of 5500 N is sufficient to move the sled with a maximum static friction of 5145 N.

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

    What is the coefficient of static friction if the force required to move a 2 kg brick is 11.8 N?

    <p>0.602</p> Signup and view all the answers

    The normal force on an object is also known as the ______.

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

    If a 4 kg object requires a 20 N force to start moving, what is the magnitude of the static friction?

    <p>20 N</p> Signup and view all the answers

    The kinetic friction is always greater than static friction.

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

    What is the formula used to calculate the coefficient of kinetic friction?

    <p>μK = Fk / η</p> Signup and view all the answers

    Match the following forces with their definitions:

    <p>Static Friction = Force that prevents the motion of stationary objects Kinetic Friction = Force opposing the motion of moving objects Normal Force = Force exerted by a surface perpendicular to an object Applied Force = Force applied to an object to move it</p> Signup and view all the answers

    What causes parcels to slide across the seat when a car turns a corner?

    <p>Inertia of the parcels</p> Signup and view all the answers

    When a bus accelerates, passengers are pushed forward due to inertia.

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

    What is the effect of a rocket's engines being switched off in space?

    <p>The rocket continues to move at constant velocity.</p> Signup and view all the answers

    The relationship between force, mass, and acceleration is described by _____ law.

    <p>Newton's Second</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Inertia = The tendency of an object to resist changes in motion Acceleration = The rate of change of velocity Force = An interaction that changes the motion of an object Mass = The amount of matter in an object</p> Signup and view all the answers

    If a force of 2 N is applied to a 1 kg mass, what will happen when 10 N is applied to a different 1 kg mass?

    <p>The 10 N mass will move further</p> Signup and view all the answers

    Mass does not affect acceleration when a constant force is applied.

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

    What two variables affect acceleration in the trolley experiment?

    <p>Force applied and mass of the object.</p> Signup and view all the answers

    What is the value of the kinetic friction coefficient (μK) when a force of 30 N causes a block to accelerate at 2.5 m/s²?

    <p>0.4</p> Signup and view all the answers

    According to Newton's Third Law, action and reaction forces act on the same object.

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

    What is the acceleration of a block pulled up a frictionless surface with a force of 7200 N, given a mass of 600 kg?

    <p>12 m/s²</p> Signup and view all the answers

    When a person walks, their foot exerts a force backwards on the floor, which is called _____ force.

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

    Match the following scenarios with their corresponding action and reaction pairs:

    <p>Walking = Foot on floor, Floor on foot Pressing against a wall = Boy on wall, Wall on boy Space rockets = Gases on chamber, Chamber on gases</p> Signup and view all the answers

    If a 3 kg block slides down a rough inclined plane with a frictional force of 15 N at an angle of 50°, what is the acceleration of the block?

    <p>4 m/s²</p> Signup and view all the answers

    A rocket can be propelled in a vacuum based solely on the reaction of gases escaping from its combustion chamber.

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

    What is the net force acting on a block if the applied force is 30 N and the friction force is 15 N?

    <p>15 N</p> Signup and view all the answers

    Study Notes

    Pushing and Pulling

    • Pushing increases the normal force since the vertical component of the pushing force acts in the same direction as gravity
    • Pulling reduces the normal force because the vertical component of the pulling force opposes gravity
    • The normal force is greater than the force of gravity when pushing
    • The normal force is less than the force of gravity when pulling

    Finding the Components of Forces

    • To resolve a force into its components, find its component in a certain direction
    • The components of a force are normally at 90 degrees to each other
    • For a force R with an angle ϴ with the horizontal, the vertical component is R sinϴ
    • For a force R with an angle ϴ with the horizontal, the horizontal component is R cosϴ

    Resultant of Multiple Forces using Components

    • To resolve a force into its horizontal and vertical components, use trigonometry
    • To find the net force, find the vector sum of all the x-components and y-components
    • The resultant (net) force is the vector sum of the x-components and y-components

    Newton's Laws

    • A force is a push or pull that causes or tends to cause a change in the state of rest or motion of a body
    • Forces do not always cause motion; they may be in equilibrium with an opposing force like friction
    • A force can act even if there is no change in motion
    • Galileo's experiment shows that a ball rolling down a slope accelerates due to gravity
    • If a car goes around a corner, the parcels slide across the seat in the opposite direction because they continue to travel in a straight line at constant velocity due to inertia
    • When a bus accelerates forwards, the passengers are 'jerked' backwards because they continue at constant velocity due to their inertia and appear to move backwards relative to the bus
    • A space rocket can continue to move at constant velocity in space even with their engines off because there are no friction forces to slow it down

    Newton's Second Law

    • Newton's Second Law describes an object's motion when a force is applied
    • Mass is the amount of matter in a body
    • Acceleration is the change in state of motion of a body
    • An applied force causes acceleration
    • Acceleration is the rate of change of velocity

    The Trolley Experiment

    • The trolley experiment demonstrates how acceleration is affected by the force and the mass of the object
    • The trolley experiment should be performed with minimal friction.

    Newton's Third Law

    • When one object exerts a force on another, the second object exerts a force of equal magnitude and opposite direction on the first object
    • These forces are always action/reaction pairs
    • Action/reaction pairs act on different objects and do not balance each other
    • Example: When walking, the foot exerts a force backwards on the floor, the floor exerts an opposing force against the foot
    • Example: When pressing against a wall, the boy exerts a force forwards, the wall exerts an opposing force on the boy
    • Example: When a rocket is propelling itself, the expanding gases experience a downwards force, the rocket experiences an upwards force
    • Rockets do not propel themselves by pushing on air, so they can operate in a vacuum

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    Description

    This quiz explores the concepts of pushing and pulling forces as well as how to find the components of forces. It covers the effects of these forces on normal force and introduces the method for calculating the resultant of multiple forces using trigonometry. Test your understanding of these fundamental topics in physics.

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