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 physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

It becomes easier to open or close a door turning about its hinges if the force is applied at the:

  1. Two third of the door

  2. Free edge of the door

  3. Middle of the door

  4. Point near the hinges
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Torque acting about any point O         $\tau _o = rF$                 for $sin\theta = 1$

where $r$ is the distance of the application of force from point O.
As  $r$ is maximum when a force is applied at the free end of the door, thus less amount of force is required to produce the same torque. Hence it is easier to open or close the door if force is applied at its free end. 

Multiple choice physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

The angular momentum of body remains conserve if:

  1. applied force on body is zero

  2. applied torque on body is zero.

  3. applied force on body is constant

  4. applied torque on body is constant.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Just as linear momentum is conserved when there is no net external forces$,$

angular momentum is constant or conserved when the net torque is zero$.$
Hence,
option $(B)$ is correct answer.

Multiple choice physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

A body is acted upon by two unequal forces in opposite directions, but not in same line. The effect is that:

  1. the body will have only the rotational motion.

  2. the body will have only the translational motion.

  3. the body will have neither the rotational motion nor the translational motion.

  4. the body will have rotational as well as translational motion.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Due to unequal forces, the net force will act on the body, so the forces are unbalanced and the unbalanced forces cause a change in motion. This means body having translational motion.
There also be torque acting on the body due to unbalanced force. So there will be rotational motion too.

Multiple choice physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

A body is acted upon by two forces each of magnitude $F$, but in opposite directions. State the effect of the forces if both forces act at the same point of the body. Which of the following is/are true?

  1. Resultant force $=0$
  2. Moment of forces $=0$

  3. No motion

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

Here, we are applying two force in same magnitude but in opposite that is one is F and -F. Hence resultant force is $F + (-F) = 0 $. 

Hence, resultant force is zero. Here perpendicular distance is same for both the forces.
Hence, if we calculate $r \times F$ cross product. We get the same magnitude of moments but opposite in direction as force are of opposite in direction. Hence moments are also zeroes. Without any resultant and moment there will be no motion.

Multiple choice physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

A body is under the action of two equal and oppositely directed forces and the body is rotating with constant non-zero angular acceleration. Which of the following cannot be the separation between the lines of action of the forces?

  1. $1m$
  2. $0.4m$
  3. $0.25m$

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

A pair of equal and opposite forces acting on a body is called a couple.

It only gives a rotating effect to the body and the torque due to a couple is
given by $\tau = Fd$
where $F$ is equal to the  magnitude of one of the forces and 
$d$ is the distance between their points of application.
To produce a non-zero angular acceleration , the torque on the body must be non zero.
Hence , the couple can give a non-zero angular acceleration to the body
only when the distance between the points of applications of the forces is non-zero.   

Multiple choice force exerted by collision collisions work, energy and power mechanics physics

During any collision

  1. Momentum is conserved

  2. Linetic energy is conserved

  3. Both conserved

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

During any collision, the momentum is conserved but the kinetic energy is not. This is because during collision, a part of kinetic energy is converted into heat sound energies.

Multiple choice force exerted by collision collisions work, energy and power mechanics physics

For two body system, the forces they apply on each other during collision with each other are

  1. external forces on the system

  2. internal forces within the system but external forces on each body

  3. external forces on the system but internal forces on each body

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

When we consider two body as one system, any interaction between them is internal. But when we consider one body (as system), the force applied by the other body is external force.

Multiple choice force exerted by collision collisions work, energy and power mechanics physics

Line which is common normal for surfaces in contact during impact is known as

  1. Line of impact

  2. Line of collision

  3. Line of energy

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

Line which is common normal for surfaces  in contact during impact is known as line of impact. This is the line along which internal force of collision acts during impact.

Multiple choice chemistry air, winds and cyclones the concept of bernoulli's principle air exerts pressure wind and pressure variations in atmospheric pressure wind and rain uneven heating of earth

A piece of paper is kept on the table.  You have to lift it from the table by blowing high-speed air over it. In which direction will you blow the air?

  1. Sideways

  2. In the upward direction

  3. In the downward direction

  4. In the upward direction below the table
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
In order to lift the paper up from the table we need to blow air in sideways.
Multiple choice fluid dynamics option b: engineering physics physics

Choose the wrong statement.

  1. Viscous force always supports the motion.

  2. A denser fluid always more viscous than a less dense fluid.

  3. Any object cannot have a velocity after a sufficient long time more than its terminal velocity in a given fluid.

  4. If a body is at rest in a fluid then the viscous force on it is zero.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Viscous force is a frictional force which opposes the relative motion between liquid molecules. Terminal velocity is the velocity attained by the particle when net force on it becomes zero the body cannot have more velocity than terminal velocity in respective fluid.

Multiple choice standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

In a tug-of-war between the teams A and B, the rope breaks at a point which is nearer to A. Then

  1. A has applied more force

  2. B has applied more force

  3. A and B both have applied same force

  4. Neither has applied any force
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In a tug-of-war, the tension throughout the rope is uniform. If the rope breaks, it is due to a structural weakness at that point, not because one side pulled harder than the other.