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 energy and its forms introduction to work work introduction to work and energy

No work is done by a force on an object if 

  1. the force is always perpendicular to its velocity

  2. the force is always perpendicular to its acceleration

  3. the object is stationary but the point of application of the force moves on the object

  4. the object moves in such a way that the point of application of the force remains fixed.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The work done by a force F in displacing a particle through d is:
$W=\vec{F}\cdot \vec{d}=Fd\cos \theta$
If $\theta =90^o$
$W=Fd\cos 90^o=0$
Now direction of displacement is same as the direction of velocity.
So if force is always perpendicular to the velocity then no work is done.
Multiple choice relativistic mechanics option a: relativity physics

Length contraction happens only __________________.

  1. perpendicular to direction of motion

  2. along direction of motion

  3. both a and b

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to the theory of special relativity, length contraction occurs only in the direction of the relative motion between the observer and the object.

Multiple choice relativistic mechanics option a: relativity physics

Special theory of relativity treats problems involving :

  1. inertial frame of reference

  2. non-inertial frame of reference

  3. non-accelerated frame of reference

  4. accelerated frame of reference
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Einstein’s special theory of relativity is also based on two postulates, the constancy of the speed of electromagnetic radiation and the validity of physical laws in all inertial frame of reference
Multiple choice relativistic mechanics option a: relativity physics

According to special theory of relativity which one is not an absolute quantity?

  1. time

  2. mass

  3. height

  4. both a and b
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
According to classical physics time and mass are not an absolute quantity
Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

Friction is minimised by using

  1. Wheels and balI bearings

  2. More number of tyres in a car

  3. Rough surfaces

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

Answer is A.

Bearings reduce friction by providing smooth metal balls or rollers, and a smooth inner and outer metal surface for the balls to roll against. These balls or rollers 'bear' the load, allowing the device to spin smoothly.
The concept behind a bearing is very simple. Things roll better than they slide. The wheels on our car are like big bearings. If we had something like skis instead of wheels, our car would be a lot more difficult to push down the road.
That is because when things slide, the friction between them causes a force that tends to slow them down. But if the two surfaces can roll over each other, the friction is greatly reduced.

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

The force of friction on a static body ________ , if It is on a rough surface then.

  1. is always zero

  2. may be gravity.

  3. may be zero

  4. both B & C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The force of friction f is always opposite the direction the object that is moving . If the object would move, then the direction of the force of friction f will be opposite the movement. If the object would not move when there is no friction, then the force of friction is zero.Hence, though the surfaces of the object are rough the force of friction can be zero if the object would not move.

Multiple choice physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

Friction depends upon ................. of surfaces.

  1. mass.

  2. nature of body.

  3. both A & B

  4. none
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Friction depends upon mass and nature of the body of surfaces.
Friction depends partly on the smoothness of the contacting surfaces, a greater force being needed to move two surfaces past one another if they are rough than if they are smooth. However, friction decreases with smoothness only to a degree; friction actually increases between two extremely smooth surfaces because of increased attractive electrostatic forces between their atoms. 
Friction does not depend on the amount of surface area in contact between the moving bodies or (within certain limits) on the relative speed of the bodies. It does, however, depend on the magnitude of the forces holding the bodies together. 
When a body is moving over a horizontal surface, it presses down against the surface with a force equal to its weight, i.e., to the pull of gravity upon it; an increase in the weight of the body causes an increase in the amount of resistance offered to the relative motion of all the surfaces in contact.

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

While opening a tap with two fingers, the forces applied are  

  1. equal in magnitude

  2. parallel to each other

  3. opposite in direction

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

While opening a tap with two fingers, a couple should be applied which is defined as a pair of parallel equal forces acting in opposite direction about two different axis.

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

On applying a constant torque on a body-

  1. linear velocity increases

  2. angular velocity changes

  3. it will rotate with constant angular velocity

  4. it will move with constant velocity
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A constant torque applied to a rigid body results in constant angular acceleration, which causes the angular velocity to change over time.