Laws of Motion MCQ Quiz - Objective Question with Answer for Laws of Motion - Download Free PDF

The correct answer is Mass.

Key Points

• Inertia is the property of an object that resists changes in its state of motion.
• It is directly related to the mass of an object; the greater the mass, the greater the inertia.
• An object with larger mass requires more force to change its state of motion compared to an object with smaller mass.
• Newton's First Law of Motion states that an object will remain at rest or in uniform motion unless acted upon by an external force, which is a description of inertia.
• For example, a heavy truck has more inertia than a small car, making it harder to start moving or stop once in motion.

 Additional Information

• Shape
  • The shape of an object does not affect its inertia. Inertia is solely dependent on mass.
  • For example, a cube and a sphere of the same mass will have the same inertia regardless of their different shapes.
• Acceleration
  • Acceleration is the rate of change of velocity of an object, not a property that affects inertia.
  • While acceleration can change the motion of an object, it doesn't determine the object's inertia.
• Velocity
  • Velocity is the speed of an object in a particular direction, and it does not influence the inertia of the object.
  • An object's inertia remains the same irrespective of its velocity.

The correct answer is Mass.

Key Points

• Inertia is the property of an object that resists changes in its state of motion or rest.
• The inertia of an object is directly proportional to its mass; the greater the mass, the greater the inertia.
• Mass is a measure of the quantity of matter in an object, and it determines how difficult it is to change the object's motion.
• Inertia is independent of other properties like shape, velocity, or acceleration.
• This fundamental concept is explained in Newton's First Law of Motion, which states that an object will remain at rest or in uniform motion unless acted upon by an external force.

Additional Information

• Newton's First Law of Motion: Also known as the Law of Inertia, it describes how an object will not change its motion unless acted upon by an external force.
• Types of Inertia:
  • Inertia of Rest: The tendency of an object to remain at rest.
  • Inertia of Motion: The tendency of an object to maintain its motion.
  • Inertia of Direction: The tendency of an object to maintain its direction of motion.
• Mass vs. Weight: Mass is an intrinsic property of an object, while weight is the force exerted by gravity on that mass (Weight = Mass × Gravitational Acceleration).
• Practical Examples of Inertia:
  • A passenger tends to move forward when a vehicle suddenly stops due to the inertia of motion.
  • A book lying on a table remains stationary unless pushed, due to the inertia of rest.
• Relation with Force: To overcome an object's inertia, a force proportional to its mass and desired acceleration must be applied (F = ma, as per Newton's Second Law).

CONCEPT:

Kinematics and Vector Addition

• The displacement of an object is a vector quantity that has both magnitude and direction.
• When a vehicle accelerates from rest, the distance traveled can be calculated using the kinematic equation:

  s = ut + (1/2)at²

• For vector addition, the net displacement can be found by combining the displacements in each direction using the Pythagorean theorem.

EXPLANATION:

• First phase:

  Acceleration = 2 m/s² towards east

  Time = 10 s

  Initial velocity (u) = 0 (starting from rest)

  Distance traveled towards east (s_east) = ut + (1/2)at²

  • = 0 + (1/2) * 2 m/s² * (10 s)²
  • = (1/2) * 2 * 100
  • = 100 meters
• Second phase:

  Acceleration = 4√2 m/s² towards south

  Time = 10 s

  Distance traveled towards south (s_south) = ut + (1/2)at²

  • = 0 + (1/2) * 4√2 m/s² * (10 s)²
  • = (1/2) * 4√2 * 100
  • = 200√2 meters
• Net displacement:

  Use the Pythagorean theorem to find the resultant displacement (d):

  • d = √(s_east² + s_south²)
  • = √(100² + (200√2)²)
  • = √(10000 + 80000)
  • = √90000
  • = 300 meters

Therefore, the net displacement of the vehicle from the starting point is 300 meters.

CONCEPT:

Retarding Force (F_retard)

F_retard = m x a

a = (v - u) / t

EXPLANATION:

• Given data:
  • Mass of the car (m) = 1000 kg
  • Initial velocity (u) = 72 km/h = 72 * (1000/3600) m/s = 20 m/s
  • Final velocity (v) = 0 m/s
  • Time taken to stop (t) = 0.2 s

• a = (v - u) / t
• = (0 - 20) / 0.2
• = -20 / 0.2
• = -100 m/s²

• F_retard = m * a
• = 1000 kg * (-100 m/s²)
• = -100,000 N
• The negative sign indicates that the force is in the opposite direction of the motion. The magnitude of the retarding force is:
  • 100,000 N or 100 kN

Therefore, the retarding force applied on the car to stop it is 100 kN.

The correct answer is Net external force on body.

Key Points

• In the second law of motion, F = ma, F represents the net external force acting on a body.
• The second law of motion states that the acceleration of a body is directly proportional to the net external force applied to it and inversely proportional to its mass.
• This law is expressed mathematically as F = ma, where 'F' is the net external force, 'm' is the mass of the body, and 'a' is the acceleration.
• Net external force is the vector sum of all the external forces acting on a body, excluding internal forces.
• The direction of the acceleration is the same as the direction of the net external force.

Additional Information

• Newton's Laws of Motion
  • Sir Isaac Newton formulated three laws of motion that describe the relationship between the motion of an object and the forces acting on it.
  • The first law, also known as the law of inertia, states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an external force.
  • The third law states that for every action, there is an equal and opposite reaction.
• Force
  • Force is a vector quantity that causes an object to move or change its velocity.
  • It is measured in newtons (N) in the International System of Units (SI).
• Mass
  • Mass is a measure of the amount of matter in an object.
  • It is a scalar quantity and is measured in kilograms (kg) in the SI unit.
• Acceleration
  • Acceleration is the rate of change of velocity of an object with respect to time.
  • It is a vector quantity and is measured in meters per second squared (m/s²) in the SI unit.

The correct answer is Mass.

Key Points

• Inertia is the property of an object that resists changes in its state of motion.
• It is directly related to the mass of an object; the greater the mass, the greater the inertia.
• An object with larger mass requires more force to change its state of motion compared to an object with smaller mass.
• Newton's First Law of Motion states that an object will remain at rest or in uniform motion unless acted upon by an external force, which is a description of inertia.
• For example, a heavy truck has more inertia than a small car, making it harder to start moving or stop once in motion.

 Additional Information

• Shape
  • The shape of an object does not affect its inertia. Inertia is solely dependent on mass.
  • For example, a cube and a sphere of the same mass will have the same inertia regardless of their different shapes.
• Acceleration
  • Acceleration is the rate of change of velocity of an object, not a property that affects inertia.
  • While acceleration can change the motion of an object, it doesn't determine the object's inertia.
• Velocity
  • Velocity is the speed of an object in a particular direction, and it does not influence the inertia of the object.
  • An object's inertia remains the same irrespective of its velocity.

The correct answer is Mass.

Key Points

• Inertia is the property of an object that resists changes in its state of motion or rest.
• The inertia of an object is directly proportional to its mass; the greater the mass, the greater the inertia.
• Mass is a measure of the quantity of matter in an object, and it determines how difficult it is to change the object's motion.
• Inertia is independent of other properties like shape, velocity, or acceleration.
• This fundamental concept is explained in Newton's First Law of Motion, which states that an object will remain at rest or in uniform motion unless acted upon by an external force.

Additional Information

• Newton's First Law of Motion: Also known as the Law of Inertia, it describes how an object will not change its motion unless acted upon by an external force.
• Types of Inertia:
  • Inertia of Rest: The tendency of an object to remain at rest.
  • Inertia of Motion: The tendency of an object to maintain its motion.
  • Inertia of Direction: The tendency of an object to maintain its direction of motion.
• Mass vs. Weight: Mass is an intrinsic property of an object, while weight is the force exerted by gravity on that mass (Weight = Mass × Gravitational Acceleration).
• Practical Examples of Inertia:
  • A passenger tends to move forward when a vehicle suddenly stops due to the inertia of motion.
  • A book lying on a table remains stationary unless pushed, due to the inertia of rest.
• Relation with Force: To overcome an object's inertia, a force proportional to its mass and desired acceleration must be applied (F = ma, as per Newton's Second Law).

CONCEPT:

Retarding Force (F_retard)

F_retard = m x a

a = (v - u) / t

EXPLANATION:

• Given data:
  • Mass of the car (m) = 1000 kg
  • Initial velocity (u) = 72 km/h = 72 * (1000/3600) m/s = 20 m/s
  • Final velocity (v) = 0 m/s
  • Time taken to stop (t) = 0.2 s

• a = (v - u) / t
• = (0 - 20) / 0.2
• = -20 / 0.2
• = -100 m/s²

• F_retard = m * a
• = 1000 kg * (-100 m/s²)
• = -100,000 N
• The negative sign indicates that the force is in the opposite direction of the motion. The magnitude of the retarding force is:
  • 100,000 N or 100 kN

Therefore, the retarding force applied on the car to stop it is 100 kN.

The correct answer is Net external force on body.

Key Points

• In the second law of motion, F = ma, F represents the net external force acting on a body.
• The second law of motion states that the acceleration of a body is directly proportional to the net external force applied to it and inversely proportional to its mass.
• This law is expressed mathematically as F = ma, where 'F' is the net external force, 'm' is the mass of the body, and 'a' is the acceleration.
• Net external force is the vector sum of all the external forces acting on a body, excluding internal forces.
• The direction of the acceleration is the same as the direction of the net external force.

Additional Information

• Newton's Laws of Motion
  • Sir Isaac Newton formulated three laws of motion that describe the relationship between the motion of an object and the forces acting on it.
  • The first law, also known as the law of inertia, states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an external force.
  • The third law states that for every action, there is an equal and opposite reaction.
• Force
  • Force is a vector quantity that causes an object to move or change its velocity.
  • It is measured in newtons (N) in the International System of Units (SI).
• Mass
  • Mass is a measure of the amount of matter in an object.
  • It is a scalar quantity and is measured in kilograms (kg) in the SI unit.
• Acceleration
  • Acceleration is the rate of change of velocity of an object with respect to time.
  • It is a vector quantity and is measured in meters per second squared (m/s²) in the SI unit.

CONCEPT:

Kinematics and Vector Addition

• The displacement of an object is a vector quantity that has both magnitude and direction.
• When a vehicle accelerates from rest, the distance traveled can be calculated using the kinematic equation:

  s = ut + (1/2)at²

• For vector addition, the net displacement can be found by combining the displacements in each direction using the Pythagorean theorem.

EXPLANATION:

• First phase:

  Acceleration = 2 m/s² towards east

  Time = 10 s

  Initial velocity (u) = 0 (starting from rest)

  Distance traveled towards east (s_east) = ut + (1/2)at²

  • = 0 + (1/2) * 2 m/s² * (10 s)²
  • = (1/2) * 2 * 100
  • = 100 meters
• Second phase:

  Acceleration = 4√2 m/s² towards south

  Time = 10 s

  Distance traveled towards south (s_south) = ut + (1/2)at²

  • = 0 + (1/2) * 4√2 m/s² * (10 s)²
  • = (1/2) * 4√2 * 100
  • = 200√2 meters
• Net displacement:

  Use the Pythagorean theorem to find the resultant displacement (d):

  • d = √(s_east² + s_south²)
  • = √(100² + (200√2)²)
  • = √(10000 + 80000)
  • = √90000
  • = 300 meters

Therefore, the net displacement of the vehicle from the starting point is 300 meters.

The correct answer is there is an equal and opposite reaction and they act on two different bodies.

Key Points

• Newton's third law states: "For every action, there is an equal and opposite reaction."
• The action and reaction forces act on two different bodies.
• This law explains the principle of conservation of momentum in isolated systems.
• The equal and opposite forces are of the same type (e.g., both are gravitational, electromagnetic, etc.).

Additional Information

• Newton's Laws of Motion:
  • First Law: An object remains at rest or in uniform motion unless acted upon by a net external force (law of inertia).
  • Second Law: The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass (F = ma).
• Applications:
  • Rocket propulsion: Exhaust gases exert a force on the rocket, and the rocket exerts an equal and opposite force on the gases.
  • Walking: When you push the ground backward with your foot, the ground pushes you forward with an equal and opposite force.
• Conservation of Momentum:
  • In a closed system, the total momentum before and after an event remains constant.
  • Newton's third law is fundamental to the principle of conservation of momentum.
• Examples in Nature:
  • Birds flying: Wings push air downwards and backwards, and air pushes wings upwards and forwards.
  • Swimming: Swimmers push water backwards with their hands and feet, and water pushes them forward.

The correct answer is Mass.

Key Points

• Inertia is the property of an object that resists changes in its state of motion.
• It is directly related to the mass of an object; the greater the mass, the greater the inertia.
• An object with larger mass requires more force to change its state of motion compared to an object with smaller mass.
• Newton's First Law of Motion states that an object will remain at rest or in uniform motion unless acted upon by an external force, which is a description of inertia.
• For example, a heavy truck has more inertia than a small car, making it harder to start moving or stop once in motion.

 Additional Information

• Shape
  • The shape of an object does not affect its inertia. Inertia is solely dependent on mass.
  • For example, a cube and a sphere of the same mass will have the same inertia regardless of their different shapes.
• Acceleration
  • Acceleration is the rate of change of velocity of an object, not a property that affects inertia.
  • While acceleration can change the motion of an object, it doesn't determine the object's inertia.
• Velocity
  • Velocity is the speed of an object in a particular direction, and it does not influence the inertia of the object.
  • An object's inertia remains the same irrespective of its velocity.

The correct answer is Only (C).

Key Points

• Equation (C), \((v-u)=at\), is derived from the basic definition of acceleration: acceleration (a) is the rate of change of velocity with time (t).
• This equation applies directly to uniformly accelerated motion, such as that of a freely falling object under gravity.
• It relates the final velocity (v) of an object to its initial velocity (u), acceleration (a), and the time of travel (t).
• Equations (A) and (B) are not correctly written or applicable in the context of a freely falling object.

Additional Information

• Equations of Motion:
  • There are three primary equations of motion that describe the behavior of objects in uniformly accelerated linear motion:
    • \(v=u+at\)
    • \(s=ut+\frac{1}{2}at^2\)
    • \(v^2=u^2+2as\)
  • These equations are essential in classical mechanics and are used to predict future motion based on current conditions.
• Uniform Acceleration:
  • Uniform acceleration refers to a constant acceleration, meaning the velocity of the object changes at a constant rate.
  • In the case of free fall, the acceleration due to gravity (g) is approximately 9.81 m/s² near the Earth's surface.
• Free Fall:
  • Free fall is the motion of an object under the influence of gravitational force only.
  • During free fall, the only force acting on the object is gravity, leading to a uniform acceleration downwards.
• Initial and Final Velocity:
  • Initial velocity (u) is the velocity of the object before it starts accelerating.
  • Final velocity (v) is the velocity of the object after it has been accelerating for a certain period of time.

The correct answer is The second law of motion is a scalar law.

Key Points

• Newton’s second law of motion is a vector law, not a scalar law, as it deals with quantities like force and acceleration, which have both magnitude and direction.
• The mathematical expression of the second law is F = ma, where 'F' and 'a' are vectors, and 'm' is a scalar quantity representing mass.
• This law is applicable to a single point particle, describing how a force acting on it results in acceleration in the direction of the force.
• The second law is a local relation, meaning the force 'F' at a specific point in space and time is directly related to the acceleration 'a' at that point and time.
• According to the second law, if the net external force (F) acting on a system is zero, the acceleration (a) of the system is also zero, implying the system is in equilibrium or moving at a constant velocity.

Additional Information

• Newton's Second Law of Motion:
  • It states that the rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction of the force.
  • The equation is written as F = ma, where F is the net force, m is the mass of the object, and a is the acceleration.
• Vector Quantities:
  • These are physical quantities that have both magnitude and direction, such as force, velocity, acceleration, and displacement.
  • Newton's second law inherently involves vector quantities, as force and acceleration must be aligned.
• Scalar Quantities:
  • These are quantities that only have magnitude and no direction, such as mass, speed, energy, and temperature.
  • Newton's second law is not scalar because it involves directional properties.
• Applications of Newton's Second Law:
  • It is widely used in engineering and physics to design vehicles, structures, and machinery by calculating forces and accelerations.
  • It also explains everyday phenomena like why heavier objects are harder to accelerate compared to lighter ones.

The correct answer is Mass.

Key Points

• Inertia is the property of an object that resists changes in its state of motion or rest.
• The inertia of an object is directly proportional to its mass; the greater the mass, the greater the inertia.
• Mass is a measure of the quantity of matter in an object, and it determines how difficult it is to change the object's motion.
• Inertia is independent of other properties like shape, velocity, or acceleration.
• This fundamental concept is explained in Newton's First Law of Motion, which states that an object will remain at rest or in uniform motion unless acted upon by an external force.

Additional Information

• Newton's First Law of Motion: Also known as the Law of Inertia, it describes how an object will not change its motion unless acted upon by an external force.
• Types of Inertia:
  • Inertia of Rest: The tendency of an object to remain at rest.
  • Inertia of Motion: The tendency of an object to maintain its motion.
  • Inertia of Direction: The tendency of an object to maintain its direction of motion.
• Mass vs. Weight: Mass is an intrinsic property of an object, while weight is the force exerted by gravity on that mass (Weight = Mass × Gravitational Acceleration).
• Practical Examples of Inertia:
  • A passenger tends to move forward when a vehicle suddenly stops due to the inertia of motion.
  • A book lying on a table remains stationary unless pushed, due to the inertia of rest.
• Relation with Force: To overcome an object's inertia, a force proportional to its mass and desired acceleration must be applied (F = ma, as per Newton's Second Law).