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

The correct answer is Newton's first law.

Key Points

• Newton's laws of motion-
  • ​Newton’s first law states that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by force.
    • This postulate is known as the law of inertia. The law of inertia was first formulated by Galileo Galilei for horizontal motion on Earth and was later generalized by René Descartes.
    • Before Galileo, it had been thought that all horizontal motion required a direct cause. Still, Galileo deduced from his experiments that a body in motion would remain in motion unless a force (such as friction) caused it to come to rest.
  • Newton’s second law is a quantitative description of the changes that a force can produce in a body's motion.
    • It states that the time rate of change of a body's momentum is equal in both magnitude and direction to the force imposed on it.
    • The momentum of a body is equal to the product of its mass and its velocity. Momentum, like velocity, is a vector quantity, having both magnitude and direction.
    • A force applied to a body can change the magnitude of the momentum, direction, or both.
    • For a body whose mass m is constant, it can be written in F = ma, where F (force) and an (acceleration) are vector quantities.
    • If a body has a net force acting on it, it is accelerated by the equation. Conversely, if a body is not accelerated, there is no net force acting on it.
  • Newton’s third law states that when two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction.
  • The third law is also known as the law of action and reaction. This law is important in analyzing static equilibrium problems, where all forces are balanced, but it also applies to bodies in uniform or accelerated motion.
  • The forces it describes are real ones, not mere bookkeeping devices. For example, a book resting on a table applies a downward force equal to its weight on the table.
  • According to the third law, the table applies an equal and opposite force to the book. This force occurs because the book's weight causes the table to deform slightly so that it pushes back on the book like a coiled spring.

The Correct answer is Statements I, II, and III are correct.

Key Points

• Linear motion is defined as the motion of an object along a straight line. This is a type of motion where all parts of the object move in the same direction and cover the same distance in a given time.
• Circular motion involves objects moving along a circular path. This type of motion is common in objects like planets orbiting stars or a car turning around a circular track.
• Oscillatory motion is characterized by a body moving to and fro about a fixed or equilibrium point. Examples include a pendulum, a vibrating tuning fork, or a spring-mass system.
• Each of these types of motion is distinct and represents a fundamental concept in the study of mechanics.
• All three statements (I, II, and III) accurately describe these specific types of motion, making them correct in this context.

Additional Information

• Linear motion
  • Examples: A car moving on a straight road, a ball rolling down an inclined plane.
  • This motion can be classified as either uniform (constant speed) or non-uniform (changing speed).
  • It is governed by fundamental principles such as Newton's laws of motion.
• Circular motion
  • Examples: A satellite orbiting the Earth, a stone tied to a string and whirled in a circle.
  • Circular motion can be classified as uniform (constant speed) or non-uniform (changing speed).
  • Key concepts such as centripetal force and centrifugal force are associated with circular motion.
• Oscillatory motion
  • Examples: Motion of a swing, vibrations of a guitar string.
  • Oscillatory motion is often periodic, meaning it repeats itself after a certain interval of time.
  • It is closely related to the study of waves and harmonic motion.

The correct answer is Both their masses and initial velocities.

Key Points

• In an elastic collision, both momentum and kinetic energy are conserved.
• The final velocities of the colliding objects are influenced by their initial velocities and masses.
• The equations governing elastic collisions are derived from the conservation laws.
• The ratio of the velocities after the collision is a function of both the masses and initial velocities of the objects.
• This dependency ensures that the system's total energy and momentum remain constant before and after the collision.

Additional Information

• Elastic Collision: A collision where there is no net loss in kinetic energy in the system as a result of the collision.
• Conservation of Momentum: The total momentum of a closed system remains constant over time.
• Conservation of Kinetic Energy: In an elastic collision, the total kinetic energy of the system before and after the collision is the same.
• Relative Velocity: The velocity of one body with respect to another. In elastic collisions, the relative velocity of approach before collision is equal to the relative velocity of separation after collision.
• Initial Velocities: The velocities of the colliding objects before the collision occurs.

The correct answer is A is correct, but R is incorrect..

Key Points

• In circular motion, the acceleration of an object is always directed towards the center of the circle; this acceleration is known as centripetal acceleration.
• Centripetal acceleration is necessary to change the direction of the velocity of the object, keeping it moving in a circular path.
• The magnitude of centripetal acceleration is given by ac=v2r" id="MathJax-Element-1-Frame" role="presentation" style="position: relative;" tabindex="0">ac=v2r ac=v2r $a_c = \frac{v^2}{r}$ , where $v$ is the velocity of the object and $r$ is the radius of the circular path.
• The reason (R) stating that the velocity of the object is constant is incorrect because, in uniform circular motion, only the speed remains constant, while the direction of velocity continuously changes.

Additional Information

• Centripetal Force:
  • It is the force that acts on an object moving in a circular path, directed towards the center of the circle, causing centripetal acceleration.
  • Examples include the gravitational force acting on planets in orbit and the tension in a string for an object moving in a circular motion.
• Uniform Circular Motion:
  • It refers to the motion of an object traveling at a constant speed along a circular path.
  • While the speed remains constant, the velocity is not constant due to the continuous change in direction.
• Tangential Velocity:
  • It is the linear speed of an object moving along a circular path.
  • Tangential velocity is always perpendicular to the radius of the circular path at any given point.
• Centripetal vs. Centrifugal Force:
  • Centripetal force acts towards the center of the circle, keeping the object in circular motion.
  • Centrifugal force is an apparent force that acts outward on an object moving around a center, arising from the object's inertia.

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 Newton's first law.

Key Points

• Newton's laws of motion-
  • ​Newton’s first law states that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by force.
    • This postulate is known as the law of inertia. The law of inertia was first formulated by Galileo Galilei for horizontal motion on Earth and was later generalized by René Descartes.
    • Before Galileo, it had been thought that all horizontal motion required a direct cause. Still, Galileo deduced from his experiments that a body in motion would remain in motion unless a force (such as friction) caused it to come to rest.
  • Newton’s second law is a quantitative description of the changes that a force can produce in a body's motion.
    • It states that the time rate of change of a body's momentum is equal in both magnitude and direction to the force imposed on it.
    • The momentum of a body is equal to the product of its mass and its velocity. Momentum, like velocity, is a vector quantity, having both magnitude and direction.
    • A force applied to a body can change the magnitude of the momentum, direction, or both.
    • For a body whose mass m is constant, it can be written in F = ma, where F (force) and an (acceleration) are vector quantities.
    • If a body has a net force acting on it, it is accelerated by the equation. Conversely, if a body is not accelerated, there is no net force acting on it.
  • Newton’s third law states that when two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction.
  • The third law is also known as the law of action and reaction. This law is important in analyzing static equilibrium problems, where all forces are balanced, but it also applies to bodies in uniform or accelerated motion.
  • The forces it describes are real ones, not mere bookkeeping devices. For example, a book resting on a table applies a downward force equal to its weight on the table.
  • According to the third law, the table applies an equal and opposite force to the book. This force occurs because the book's weight causes the table to deform slightly so that it pushes back on the book like a coiled spring.

The correct answer is 342 m.

CONCEPT:

• Echo: If we shout or clap near a suitable reflecting object such as a tall building or a mountain, we will hear the same sound again a little later. This sound which we hear is called an echo.
  • Echoes are heard due to the phenomenon of Reflection of sound waves.
  • To hear the echo clearly, the reflecting object must be more than 17.2 m from the sound source for the echo to be heard by a person standing at the source.

CALCULATION:

Speed of sound = 342 m/s.

The time is taken for hearing an echo = 2s.​

• The speed of sound is

\(⇒ Speed (v)= \frac{distance (d)}{time (t)}\)

Distance travelled = 2d = v × t

⇒ 2 × d = 342 × 2

⇒ d = (342 × 2)/2

The correct answer is To increase friction.

CONCEPT:

• Friction: Friction is a contact force when two surfaces interact. 
• Friction, a force that resists the sliding or rolling of one solid object over another.

EXPLANATION:

• Insoles of the shoes, they are treated to make their surface rough so that the frictional force is increased when they are used.
• The tyres of the vehicle are also treaded to increase friction and prevent slipping.
• For example, tires are treaded to reduce the risk of slipping and increase friction during the rainy or wet road, the same case is true for treaded shoes.

Important Points

• Friction finds application during matchsticks are ignited.
• The motion of pistons in a cylinder is an application of friction.
• It is possible to write on books and board because there is friction between the pen and the board.

The correct answer is Speed is constant.

Key Points

• Circular motion is a movement of an object along the circumference of a circle or rotation along a circular path.
• The distance and displacement are different at every instance at any particular point of time.

Confusion Points

• While the speed is a scalar quantity, in uniform motion, it remains constant.
• As, Velocity is a vector quantity, and the direction of movement changes continuously, velocity changes continuously.
• Due to this, the object is in accelerated motion.

Important Points

About the Circular Motion:

• As the direction of the velocity changes at every instant, it is an accelerated motion.
• During the motion, the particle repeats it's paths along the same trajectory.
• Thus the motion is periodic.

Uniform Circular Motion:

• During circular motion, if the speed of the period remains constant, it is a Uniform Circular Motion. Hence option 4 is correct.

CONCEPT:

• Work-energy theorem: It states that the sum of work done by all the forces acting on a body is equal to the change in the kinetic energy of the body i.e.,

Work done by all the forces = Kf - Ki

\(W = \frac{1}{2}m{v^2} - \frac{1}{2}m{u^2} = {\bf{Δ }}K \)

Where v = final velocity, u = initial velocity and m = mass of the body

CALCULATION:

It is given that,
Mass (m) = 4.0 kg

Final Velocity (v) = 5 m/s and initial velocity (u) = 0 m/s
According to the work-energy theorem,

⇒  Work done = Change in K.E
⇒  W = Δ K.E

Since initial speed is zero so the initial KE will also be zero.

⇒  Work done (W) = Final K.E = 1/2 mv²
⇒  W = 1/2 × 4 × 5²
⇒  W = 2 × 25
⇒  W = 50 J

The Correct Answer is 125 m.

Concept:

• The average acceleration for a given interval is defined as the velocity change for that particular interval of time.
• Unlike acceleration, for a given interval the average acceleration is determined.

\(a=\frac{\Delta v}{\Delta t}\)

Δv = Change in velocity

Δt = The duration of the period

Calculations:

Given that,

The initial velocity u = 18 km/h = 5 m/s

The final velocity v = 72 km/h = 20 m/s

Since the answer must be in m so, we need to convert

• Conversion of km/hr to m/s and vice versa-

18 km/hr converted to 18 × (5/18) = 5m/s

72 km/hr converted to 72 × (5/18) = 20 m/s

Time  = 10 sec

To find the distance travelled by car, we need to find acceleration,

\(a=\frac{\Delta v}{\Delta t}=\frac{change\; in\; velocity}{time}=\frac{20-5}{10}=1.5\;ms^{-2}\)

a = 1.5 m/s²

The distance travelled by car, we use the 2^nd equation of motion,

\(s=ut+\frac{1}{2}at^{2}\)

\(s=(5\times 10)+\frac{1}{2}(1.5)\times 10^{2}\)

s = (50 + 75) m

s = 125 m

The distance travelled by car is 125 m.

• The first equation of motion gives the relation between "velocity and time".
• The first equation of motion is v = u +at.
• Here, v is the final velocity, u is the initial velocity, a is the acceleration and t is the time.
• The velocity-time relation gives the first equation of motion and can be used to find acceleration.
• The position-time relation gives the second equation of motion, i.e. s = ut + (1/2) at²
• The position-velocity relation gives the third equation of motion, i.e. v² = u² +2as

Mass of body (m) = 50 kg

Acceleration (a) = 8 m/sec²

Time (t) = 15 seconds

According to kinematics equation, assuming acceleration is constant,

S = u t + 1/2 a t2 

Where

S = Distance travelled by the body (m)

u = Initial velocity (m/s)

a = Acceleration (m/s²)

t = Time taken

As body starts from rest u = 0 i.e. Initial velocity.

S = 0 + (1/2) × 8 × 15²  = 900m

S = 900 metres

The correct answer is Newton's first law.

CONCEPT:

• Newton’s first law of motion: It is also called the law of inertia. Inertia is the ability of a body by virtue of which it opposes a change.
• According to Newton’s first law of motion, an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
• The inertia of rest: When a body is in rest, it will remain at rest until we apply an external force to move it. This property is called inertia of rest.
• The inertia of motion: When a body is in a uniform motion, it will remain in motion until we apply an external force to stop it. This property is called inertia of motion.

EXPLANATION:

• When a bus suddenly starts moving, the passengers fall backward due to the law of inertia of rest or 1st law of Newton.
• Because the body was in the state of rest and when the bus suddenly starts moving the lower body tends to be in motion, but the upper body still remains in a state of rest due to which it feels a jerk and falls backward. Hence option 1 is correct.

Additional Information

Laws of Motion given by Newton are as follows:

The correct answer is Velocity, time, and acceleration.

The first equation of motion gives the relation between initial velocity, final velocity, acceleration, and time.

• First equation of motion is given as v = u + at
  • Where, v = final velocity
  • u = initial velocity
  • a = acceleration
  • t = time taken

• The first equation of motion gives the value of velocity acquired by the body at any particular point of time t.
• The second equation of motion is given as s = ut + ½at²
• It gives the value of distance (s) traveled by a body at a given time t.
• Third equation of motion is given as v² = u² + 2as
• This equation gives the velocity of the body in traveling the distance s.