Physics · Science General

Newtonian Mechanics and Forces

1,559 Questions

Newtonian mechanics studies the motion of objects and the physical laws governing them. This hub covers friction, gravitational force, inertia, and vector quantities. Mastering these fundamental physics concepts is essential for various government competitive exams.

Laws of motionFriction and inertiaVector and scalar quantitiesGravitational accelerationArchimedes principle

Newtonian Mechanics and Forces Questions

Multiple choice

Which of the following statements is false about forces/couple?

  1. Moment of couple is free vector

  2. Resultant and equilibrant are equal in magnitude and direction

  3. Resultant of a couple is always zero

  4. Parallelogram law is to be proved experimentally
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Resultant and equilibrant are equal in magnitude and direction

Multiple choice

The ratio of static friction to dynamic friction is always

  1. Greater than one

  2. Less than one

  3. Equal to one

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Static friction is the force required to initiate motion, which is always greater than the dynamic (kinetic) friction required to maintain motion once it has started.

Multiple choice

The ratio of static friction to dynamic friction is always

  1. Greater than one

  2. Equal to one

  3. Less than one

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Static friction is the force required to initiate motion, which is always greater than the dynamic (kinetic) friction required to maintain motion once it has started.

Multiple choice physics wave motion reflection of waves

Reflection at a free boundary implies

  1. restoring force is zero

  2. restoring force is not zero

  3. applied force is zero

  4. applied force is not zero
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a free boundary, the restoring force is always zero

The correct option is (a)

Multiple choice physics satellite launch vehicles rocket propellants universe and space science xx radio telescope and space telescopes launching vehicles

Streamlining of the rocket :

  1. minimizes the friction of air.

  2. maximizes the friction of air.

  3. Either A or B is correct depending on the weight of the rocket.

  4. Both A and B.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Whenever any object moves through air, air opposes the motion. This is known as air resistance. 

The intensity of air resistance depends on the area of the surface which is perpendicular to the direction of motion.
To reduce this resistance, the face of the rocket is made almost conical. This is known as streamlining. 
Streamlining minimizes air resistance and increases the speed of the rocket. 

Multiple choice physics satellite launch vehicles rocket propellants universe and space science xx radio telescope and space telescopes launching vehicles

Blow a balloon and let it go. You will find it moving in the direction opposite to the direction in which the air is ejected. This demonstrates :

  1. the principle of rocket propulsion

  2. the principle of combustion

  3. the principle of conservation of energy

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The principle of rocket propulsion works on the 'Newton's Third Law of Motion'. It states that, 'to every action, there is always an equal and opposite reaction'.

In the case of a rocket, the engine emits hot burning gases in the downward direction. These gases apply an equal and opposite reaction force to the rocket in the upward direction.
This is how a rocket is propelled.
Rocket propulsion is similar to the example of the situation in which, if we blow a balloon and let it go, it starts moving in the direction opposite to the direction in which the air is ejected. 
Balloon forces out the air inside it. The air applies an equal and opposite reaction force to the balloon.

Multiple choice chemistry in daily life satellite launch vehicles rocket propellants

The propulsion of a rocket is based on the principle of conservation of

  1. linear momentum

  2. energy

  3. angular momentum

  4. mass
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The rocket propulsion is based on the principle of linear momentum conservation as initially the rocket is at rest but when the rocket is ready to take off the the momentum of small mass of gas ejected at high speed is compensated by increased momentum of the rocket with the remaining fuel.

Multiple choice physics satellite launch vehicles rocket propellants universe and space science xx radio telescope and space telescopes launching vehicles

The principle of rocket propulsion depends on :

  1. Newton's third law of motion

  2. Principle of conservation of momentum

  3. Either A and B

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The principle of rocket propulsion works on the 'Newton's Third Law of Motion'. It states that, 'to every action, there is always an equal and opposite reaction'.

In the case of a rocket, the engine emits hot burning gases in the downward direction. These gases apply an equal and opposite reaction force to the rocket in the upward direction.
This is how a rocket is propelled.
The principle of conservation of momentum states that whenever two bodies collide or get separated, then their  total momentum before collision or separation is equal to their total momentum after collision or separation.
Since the gases of the rocket and the rocket are stationery at the start, their total momentum is zero. After the gases start burning, the momentum imparted to the rocket is equal and opposite to that of the gases. Hence their total momentum is zero.

Multiple choice

What is the name of the force that holds you on the ground?

  1. Gravitational potential

  2. Resultant Force

  3. Weight

  4. Gravity
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Gravity is the fundamental force of attraction between masses, which holds objects on the surface of the Earth. Weight is the measure of the force of gravity acting on an object.

Multiple choice

What forces are equal in size and opposite in direction?

  1. Balanced forces

  2. Unbalanced forces

  3. Jedi's and the Dark Side

  4. Gravity
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Balanced forces are defined as forces that are equal in magnitude and opposite in direction, resulting in no net force. Unbalanced forces cause a change in motion.