Physics · Science General

Newtonian Mechanics and Forces

1,605 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

The product of mass and the velocity of a body is called

  1. displacement.

  2. speed.

  3. momentum.

  4. work.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In physics, linear momentum is defined as the product of an object's mass and its velocity (p = mv). It is a vector quantity that describes the motion of an object.

Multiple choice

Which of the following laws states that "the maximum force one's muscles can exert decreases exponentially from the time one begins to continuously exert the force"?

  1. Lyon's law

  2. Rohmert's law

  3. Dollo's law

  4. Von Baer's law
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Rohmert's law states that the maximum force one's muscles can exert decreases exponentially from the time one begins to continuously exert the force. It is used to calculate the maximum holding time for a task.

Multiple choice

The sensation of weightlessness in a spacecraft in an orbit is due to the

  1. absence of gravity outside

  2. acceleration in the orbit which is equal to the acceleration due to gravity outside

  3. presence of gravity outside but not inside the spacecraft

  4. fact that spacecraft in the orbit has no energy
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Weightlessness in orbit occurs because the spacecraft and everything inside it are in a state of continuous free fall, meaning they are accelerating toward Earth at the same rate as gravity.

Multiple choice

Newton's 1st law of motion gives the concept of

  1. energy

  2. work

  3. momentum

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

Newton's first law, also known as the law of inertia, states that an object will remain at rest or in uniform motion unless acted upon by an external force. Inertia is the inherent property of matter that resists changes in its state of motion.

Multiple choice

Friction can be reduced by changing over from

  1. dynamic to static

  2. rolling to sliding

  3. sliding to rolling

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

Rolling friction is significantly lower than sliding friction. Therefore, using wheels or ball bearings to change sliding motion into rolling motion is a standard method to reduce friction.

Multiple choice

We can hold a pen due to the

  1. Force of gravity

  2. Force of friction

  3. Force of weight

  4. Work done by our muscles
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Friction between our fingers and the surface of the pen allows us to grip and hold it securely. Without friction, the pen would slip out of our hand.

Multiple choice

A rocket works on the

  1. first law of motion

  2. second law of motion

  3. third law of motion

  4. Bernoulli Theorem
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A rocket works on Newton's third law of motion, which states that for every action, there is an equal and opposite reaction, as gas is expelled downward to push the rocket upward.

Multiple choice

It is difficult to work on ice because of

  1. absence of friction

  2. absence of inertia

  3. less inertia

  4. more friction

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ice has a very smooth surface, which results in a lack of friction. Friction is necessary for walking, as it provides the grip needed to push off the ground.

Multiple choice

The centre of mass of a body

  1. always lies outside the body

  2. always lies inside the body

  3. always lies on the surface of the body

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The centre of mass of the body may lie on the surface of the body or outside or inside the body

Multiple choice

Velocity of a body is the

  1. change of its position

  2. rate of change of its position

  3. change of its position in a definite direction

  4. rate of change of its position in a definite direction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Velocity is a vector quantity defined as the rate of change of position with respect to time in a definite direction. Unlike speed (which is scalar), velocity specifies both magnitude and direction. Option B only describes speed, while option D correctly includes both the rate aspect (speed) and the directional requirement that makes it velocity.

Multiple choice

A toy has fallen from your hands, before touching the ground it has

  1. gained kinetic energy and lost potential energy

  2. gained potential energy and lost kinetic energy

  3. gained kinetic as well as potential energy

  4. lost kinetic as well as potential energy
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As an object falls under gravity, its height decreases which reduces its gravitational potential energy (PE = mgh). This lost potential energy is converted into kinetic energy (KE = 1/2 mv^2) as the object gains speed. The total mechanical energy remains constant (ignoring air resistance), so the gain in KE exactly equals the loss in PE.

Multiple choice

Work done against friction is

  1. negative

  2. positive

  3. zero

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

Work done against friction is negative because the frictional force always acts opposite to the direction of displacement. When we calculate work as W = F·d·cos(theta), the angle between friction force and displacement is 180°, giving cos(180°) = -1. This negative work represents energy dissipated as heat.

Multiple choice

What causes an object to accelerate?

  1. Force

  2. Work

  3. Speed

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

According to Newton's second law of motion, force is the agent that causes an object to accelerate. Acceleration is defined as the rate of change of velocity, which is produced by a net force.