First Year Physics Chapter 3 Online Short Questions Preparation for 1st Year Physics Chapter 3 (Motion and Force)

Can the velocity of an object reverse the direction when acceleration is constant? If so, given an example.

• Ans 1: Yes, the velocity of a body can reverse its direction with constant acceleration For example, when a body is thrown vertically upward under the action of gravity, the velocity of the object will go on decreasing because force of gravity is acting downward.
  When the object reaches the maximum height , its velocity becomes zero, and then the object reverses its direction of motion and start moving vertically downward.During the whole process, the magnitude of the acceleration due to gravity remains constant.

Define Distance and displacement ?

• Ans 1: Distance:The length of actual path traversed by a body in motion is known as distance. The actual path may be straight or cured. The distance is a scalar quantity. Its S.I units is meter.
  Displacement:The shortest distance between is know as displacement.
  A body reaches from point 'O' to 'C' through 'A" and 'B'. Thus the path 'OABC' represents the actual path traversed by the body during its motion. So it is called distance. While 'oc' represents the shortest distance between the initial point 'o' and final point 'c' It S.I unit is meter

Find on expression for horizontal rang of projectile?

• Ans 1:

Why Newton's first law of motion is known as law of inertia?

• Ans 1: Newton's first law of motion is:
  A body at rest will remain at rest and a body moving with uniform velocity will continue to do so unless acted upon by some unbalanced external force.
  It is based on mass and inertia is the quantitative measure of an object's mass. So Newton's first law of motion is also Known as law of inertia.

Define inertial and non-inertial frame of references.

• Ans 1: Inertial Frame of References: The frame of reference in which Newton's first law holds is called inertial frame of reference. It is not an accelerated frame of reference.e.g,, Earth is approximately an inertial frame of reference.
  Non-Inertial Frame of Reference: The frame of reference in which Newton's first law does not hold true is called non-inertial frame of reference.It is an accelerated frame of reference e.g., Space ship etc.

Under what condition, the instantaneous and average velocities of a moving object become equal?

• Ans 1: For a body moving with uniform velocity, its average and instantaneous velocities are equal.

What is ballistic missile? Define ballistic trajectory.

• Ans 1: The missile in which it is given an initial push and is then allowed to move freely due to inertia and under the action of gravity is called ballistic and the path followed by such a projectile is called ballistic trajectory.

Define total of flight. Derive a mathematical expression for it ?

• Ans 1: The term taken by projectile from point of projection to the striking point is known as total time of flight.

Define linear momentum ? Express Newton,s 2nd Law in terms of momentum?

• Ans 1:

Define Collision ? Discuss the type of collision?Give example in each case?

• Ans 1: Collision:When two or more than two bodies come so closer to each other that there exists some type of interaction between them in the presence or absence of external forces then such type of interaction is known as collision.
  Type of Collision:There are two type of collision, which are given below.
  Elastic Collision:The Collision in which the momentum and kinetic energy both are conserved is known as elastic collision.
  Examples:
  1. collision of steel balls,
  2. Collision of atoms,
  3. Collision of molecules.

  Inelastic Collision:The Collision in which the momentum is conserved but K.E is not conserved, is known as Inelastic collision. "
  In such type of collision, same type of the K.E is converted into internal energy, sound energy and the work needed to permanently deform the object involed, such as cars ina car crash.
  Example:
  1. Collision between two vehicles
  2. Collision between two mud balls

What is isolated system ? State and explain the law conservation of linear momentum. with an example ?

• Ans 1: Isolated System:A system which is not affected by external forces is known as an isolated system.
  Law of conservation of linear Momentum:
  Statement:This law states that, In the absence of external forces the total linear momentum of the system remains constant.
  Example:Consider two bodies of masses 'm₁, and m₂which are moving in the same direction along the same line, as shown in the figure
  

Write any two properties of inertial frame of reference.

• Ans 1:
  1. A non-accelerated frame of reference is an inertial frame of reference.
  2. Newton's 1st law of motion holds good in an inertial frame of reference.

What are the factors upon which force due to water depend?

• Ans 1: Force due to water flow depends upon viscosity of the media and velocity of the fluid.

State law of inertia?

• Ans 1: Newton's 1stlaw of motion is called law of inertia
  It states that a body at rest will remain at rest , and a body moving with uniform velocity will continue to do so, unless acted upon by some unbalanced external force.

Distinguish between elastic and inelastic collision.

• Ans 1: In case of elastic collision the K.E of the system is conserved while in case of inelastic collision the K.E is not conserved. But the total linear momentum and the total energy of the system remains constant in both types of collision.

Find a relation for magnitude of velocity of projectile and direction of projectile?

• Ans 1:

• Ans 1:

Define free fall motion? Also define the acceleration due to gravity ?

• Ans 1: If we drop an object from certain height height 'h' and ignore the air resistance then such motion of the body is known as free fall motion. the acceleration of free fall body is known as acceleration due to gravity.
  It is represented by 'g' Its value varies with altitude and depth. On earth surface or near earth surface its value is 9.8 m/sec²

What is principle of rocket propulsion speed?

• Ans 1: Hot gases are expelled with extremely high velocity from the rocket engines.The gain in momentum of the gases equals the gain in momentum of the rocket.The gases and rocket move in opposite directions. This, the principle of rocket propulsion speed is law of conservation of momentum and Newton's 3rd law of motion.

Define inertial and non-inertial frame of references.

• Ans 1: Inertial Frame of References: The frame of reference in which Newton's first law holds is called inertial frame of reference. It is not an accelerated frame of reference.e.g,, Earth is approximately an inertial frame of reference.
  Non-Inertial Frame of Reference: The frame of reference in which Newton's first law does not hold true is called non-inertial frame of reference.It is an accelerated frame of reference e.g., Space ship etc.

State Newton's third law of motion and give at least two examples.

• Ans 1: It states that every action has a reaction which is equal in magnitude but opposite in direction.An ideal elastic collision and propulsion of a rocket are two good examples of third law of motion.

Define inertial and non-inertial frame of references.

• Ans 1: Inertial Frame of References: The frame of reference in which Newton's first law holds is called inertial frame of reference. It is not an accelerated frame of reference.e.g,, Earth is approximately an inertial frame of reference.
  Non-Inertial Frame of Reference: The frame of reference in which Newton's first law does not hold true is called non-inertial frame of reference.It is an accelerated frame of reference e.g., Space ship etc.

Define total of flight. Derive a mathematical expression for it ?

• Ans 1: The term taken by projectile from point of projection to the striking point is known as total time of flight.

Discuss the momentum changes produced by explosive forces ?

• Ans 1: There are many cases where momentum changes are produced by explosive forces within an isolated system. It can be explain with the help of following Example:
  When a sheel explodes in mind-air its fragment fly apart in different direction. the various forces which occur in the explosion have zero resultant, because they cancel the effect of each other. so the total moments of the fragments is equal to the initial momentum of the sheel.

Under what conditions a body can move with uniform acceleration?

• Ans 1: If the velocity of the body is changing equally in equal intervals of time, the body is said to have uniform acceleration.
  For a body moving with uniform acceleration, its average acceleration is equal to instantaneous acceleration.

What is isolated system ? State and explain the law conservation of linear momentum. with an example ?

• Ans 1: Isolated System:A system which is not affected by external forces is known as an isolated system.
  Law of conservation of linear Momentum:
  Statement:This law states that, In the absence of external forces the total linear momentum of the system remains constant.
  Example:Consider two bodies of masses 'm₁, and m₂which are moving in the same direction along the same line, as shown in the figure
  

Define maximum height of projectile? Derive a mathematical expression for maximum height of projectile ?

• Ans 1:

Define linear momentum ? Express Newton,s 2nd Law in terms of momentum?

• Ans 1:

State and explain Newton's second law of motion.

• Ans 1:

Discuss the condition of equilibrium ?

• Ans 1:
  Newtons 1st Law of motion: This Law states that "A body at rest will remain at rest and a body in motion will continue its motion with uniform velocity unless it is acted upon by some unbalanced external force
  If F = 0 Then a = 0
  Explanation: The Ist law of motion is also known as law of inertia. The inertia is the property of a body which opposes any change in its state of motion or rest. Actually, when some force is applied on a body for changing its state of rest or uniform motion, then the body will affer resistance against this change. In the word, We can say that all the bodies try to maintain its state of rest or continue its uniform motion due to inertia. That is the why the newtons Ist law is also known as law of inertia.
  Examples:When we give a jerk to the branch of a tree, then the fruit falls down. It is because, when we give a jerk, the branch of the tree comes into motion suddenly.
  When a bus starts motion suddenly, the passengers experience a push in the back ward direction It is because, when the bus starts motion suddenly, the lower parts of the passenger in contact with the seats also come into motion. while the upper parts of the passengers are at remain at the rest In this attempt, they falls in the back words directions
  Newton's 2nd Law of motion:
  Statements: This law states that, "when a force is applied on a body, then acceleration is produced in the body in the direction of applied force and inversely proportional to the mass of the body.
  Explanation: The Ist Law of motion gives us the quantitative measurements of force, While the 2nd law of motion gives us the quantitative measurements of forces. now if the direction of motion of the body and direction of motion of the body and direction of forces are the same, then its velocity and acceleration increases. If the direction of motion of the body and direction of force are opposite in direction of force are opposite in direction, then the velocity and acceleration of the body will decreases gradually and finally become zero and the body will come to rest
  Example of newtons 2nd law of motion:
  
  When a body falls on a solid floor from the top of a building, the body experience or feel great pain. It is because, when the body falls on the floor, its acceleration become zero suddenly and the body faces huge force for very short period of time
  Newton,s 3rd Law of motion:
  This Law states that for every action, there is always a reaction. These forces are equal in magnitude but opposite in direction.
  Explanation: This law tells us that no body can experience a force from its surrounding, until this body exerts any force on its surrounding It means That forces are exerted in pairs.

Motion with constant velocity is a special case of motion with constant acceleration.Is this statement true?

• Ans 1: Yes, this statement is true. When a body moves with constant velocity in the straight line, its acceleration is zero.Hence,The acceleration of the body will always remain constant during such motion.As the zero is a constant quantity, therefore this is a special case of motion.

How is the distance calculated from velocity time graph?

• Ans 1: Area under the velocity time graph line is equal to the distance covered by the body.

Write two object?

• Ans 1: Velocity time graph can be used to
  
  1. Calculate the distance covered by the body .
  2. Find the instantaneous acceleration of the body.

Define Impulse ? Show that impulse is equal to change in momentum show that J= P

• Ans 1: Impulse: The product of forces and duration of time in which the force acts is known as impulse.

Differentiate between distance and displacement.

• Ans 1:
  

What is the difference between uniform and variable velocity?

• Ans 1: Uniform Velocity: A body is said to have a uniform velocity if it covers equal displacement in equal intervals of time.
  
  
  Variable Velocity: A body is said to have a variable velocity if it covers unequal displacements in equal intervals of time.

State law of inertia?

• Ans 1: Newton's 1stlaw of motion is called law of inertia
  It states that a body at rest will remain at rest , and a body moving with uniform velocity will continue to do so, unless acted upon by some unbalanced external force.

Define momentum and write down its unit.

• Ans 1:

Derive its equation of motion ?

• Ans 1:

What is a Ballistic Flight?

• Ans 1: The flight in which projectile is given an initial push and is then allowed to move freely due to inertia and under the action of gravity is called ballistic flight and the path followed by it is called ballistic trajectory

Discuss the sign of acceleration due to gravity relative to velocity,while the object in in air?

• Ans 1: When the object is thrown vertically upward, it will move against the direction of gravity. The sign of acceleration due to gravity relative to velocity will be taken as negative.When the object is falling downward , it will move along the direction of gravity .
  The sign of acceleration due to gravity relative to velocity will be taken as positive.

Write any two properties of inertial frame of reference.

• Ans 1:
  1. A non-accelerated frame of reference is an inertial frame of reference.
  2. Newton's 1st law of motion holds good in an inertial frame of reference.

Discuss the condition of equilibrium ?

• Ans 1:
  Newtons 1st Law of motion: This Law states that "A body at rest will remain at rest and a body in motion will continue its motion with uniform velocity unless it is acted upon by some unbalanced external force
  If F = 0 Then a = 0
  Explanation: The Ist law of motion is also known as law of inertia. The inertia is the property of a body which opposes any change in its state of motion or rest. Actually, when some force is applied on a body for changing its state of rest or uniform motion, then the body will affer resistance against this change. In the word, We can say that all the bodies try to maintain its state of rest or continue its uniform motion due to inertia. That is the why the newtons Ist law is also known as law of inertia.
  Examples:When we give a jerk to the branch of a tree, then the fruit falls down. It is because, when we give a jerk, the branch of the tree comes into motion suddenly.
  When a bus starts motion suddenly, the passengers experience a push in the back ward direction It is because, when the bus starts motion suddenly, the lower parts of the passenger in contact with the seats also come into motion. while the upper parts of the passengers are at remain at the rest In this attempt, they falls in the back words directions
  Newton's 2nd Law of motion:
  Statements: This law states that, "when a force is applied on a body, then acceleration is produced in the body in the direction of applied force and inversely proportional to the mass of the body.
  Explanation: The Ist Law of motion gives us the quantitative measurements of force, While the 2nd law of motion gives us the quantitative measurements of forces. now if the direction of motion of the body and direction of motion of the body and direction of forces are the same, then its velocity and acceleration increases. If the direction of motion of the body and direction of force are opposite in direction of force are opposite in direction, then the velocity and acceleration of the body will decreases gradually and finally become zero and the body will come to rest
  Example of newtons 2nd law of motion:
  
  When a body falls on a solid floor from the top of a building, the body experience or feel great pain. It is because, when the body falls on the floor, its acceleration become zero suddenly and the body faces huge force for very short period of time
  Newton,s 3rd Law of motion:
  This Law states that for every action, there is always a reaction. These forces are equal in magnitude but opposite in direction.
  Explanation: This law tells us that no body can experience a force from its surrounding, until this body exerts any force on its surrounding It means That forces are exerted in pairs.

Define Collision ? Discuss the type of collision?Give example in each case?

• Ans 1: Collision:When two or more than two bodies come so closer to each other that there exists some type of interaction between them in the presence or absence of external forces then such type of interaction is known as collision.
  Type of Collision:There are two type of collision, which are given below.
  Elastic Collision:The Collision in which the momentum and kinetic energy both are conserved is known as elastic collision.
  Examples:
  1. collision of steel balls,
  2. Collision of atoms,
  3. Collision of molecules.

  Inelastic Collision:The Collision in which the momentum is conserved but K.E is not conserved, is known as Inelastic collision. "
  In such type of collision, same type of the K.E is converted into internal energy, sound energy and the work needed to permanently deform the object involed, such as cars ina car crash.
  Example:
  1. Collision between two vehicles
  2. Collision between two mud balls

State Newton's third law of motion and give at least two examples.

• Ans 1: It states that every action has a reaction which is equal in magnitude but opposite in direction.An ideal elastic collision and propulsion of a rocket are two good examples of third law of motion.

Define maximum height of projectile? Derive a mathematical expression for maximum height of projectile ?

• Ans 1:

What is projectile motion? In what direction acceleration is zero in this motion?

• Ans 1: It is the two dimensional motion in which the object moves under constant acceleration due to gravity.
  The acceleration in horizontal direction is zero in projectile motion.

Discuss the velocity-Time Graph ?

• Ans 1:

Write two object?

• Ans 1: Velocity time graph can be used to
  
  1. Calculate the distance covered by the body .
  2. Find the instantaneous acceleration of the body.

What is meant by perfectly elastic head-on-collision ?discuss the elastic collision in one dimension and find the mathematical equation for calculating the final velocities of colliding objects in one dimension?

• Ans 1: Perfectly elastic head-on-collision:The collision in which the motion of the objects occurs along a straight line is known as perfect elastic head-on-collision.Determination of mathematical equations for calculating the final velocities of colliding objects in one dimension:

Write two object?

• Ans 1: Velocity time graph can be used to
  
  1. Calculate the distance covered by the body .
  2. Find the instantaneous acceleration of the body.

State and explain Newton's second law of motion.

• Ans 1:

• Ans 1:

What is ballistic missile? Define ballistic trajectory.

• Ans 1: The missile in which it is given an initial push and is then allowed to move freely due to inertia and under the action of gravity is called ballistic and the path followed by such a projectile is called ballistic trajectory.

What are the factors upon which force due to water depend?

• Ans 1: Force due to water flow depends upon viscosity of the media and velocity of the fluid.

Show that for the same initial speed and some range of projectile there are two mutually complementary angles of projection ?

• Ans 1:

Derive the 3rd equation of motion?

• Ans 1:

Name the quantities which can be calculated from velocity-time graph and these can be calculated ?

• Ans 1: Distance moved by the body and its acceleration can be calculated by the velocity-time graph.
  Area under the velocity time graph line is equal to the distance covered by the body. Slope of the tangent at any point gives the instantaneous acceleration at that point.

Derive the 2nd equation of motion ?

• Ans 1:

Write any two properties of inertial frame of reference.

• Ans 1:
  1. A non-accelerated frame of reference is an inertial frame of reference.
  2. Newton's 1st law of motion holds good in an inertial frame of reference.