Laws of motion practice · Mixed difficulty

Assertion: Pseudo force is an imaginary force which is recognised only by a non-inertial observer to explain the physical situation according to Newton's laws.
Reason: Pseudo force has no physical origin, that is, it is not caused by one of the basic interactions in nature. It does not exist as on action reaction pair.

If impulse $I$ varies with time $t$ as $F\left(\mathrm{kg}-\mathrm{ms}^{-1}\right)=20 t^2-40 t$. The change in momentum is minimum at

An object is placed on the surface of a smooth inclined plane of inclination $\theta$. It takes time $t$ to reach the bottom of the inclined plane. If the same object is allowed to slide down rough inclined plane of same inclination $\theta$, it takes time nt to reach the bottom where $\mathrm{n}$ is a number greater than 1 . The coefficient of friction $\mu$ is given by

Select the incorrect statement(s) about static friction.
I. Static friction exists on its own
II. In the absence of applied force static friction is maximum
III. Static friction is equal and opposite to the applied force upto a certain limit

A rider on horse falls backward when horse starts running all of a sudden because of

Statement I: Limiting friction depends on surface area.
Statement II: Kinetic friction depends on surface area.

Why does a man getting down from a running bus fall forward?

The force of 6 N acts on a body at rest and of mass 1 kg. During this time the body attains a velocity of 30 m/s. The time for which the force acts on the body is

Which of the following is NOT an illustration of Newton's third law?

The rate of mass of the gas emitted from rear of a rocket is initially $0.1 \mathrm{~kg} / \mathrm{sec}$. If the speed of the gas relative to the rocket is $50 \mathrm{~m} / \mathrm{sec}$ and mass of the rocket is $2 \mathrm{~kg}$, then the acceleration of the rocket in $\mathrm{m} / \mathrm{sec}^2$ is

A body of mass M is kept on a rough horizontal surface (friction coefficient $\mu$). A person is trying to pull the body by applying a horizontal force but the body is not moving. The force by the surface on the body is F, where

Assertion(A): A glass ball is dropped on concrete floor can easily get broken compared, if it is dropped on wooden floor.

Reason(R): On concrete floor, glass ball will take less time to come to rest.

A lift is moving upwards with an acceleration $a$. The force exerted by a person of mass $M$ on the floor of the lift will be

Five persons $\mathrm{A}, \mathrm{B}, \mathrm{C}, \mathrm{D}$ and $\mathrm{E}$ are pulling a cart of mass $100 \mathrm{~kg}$ on a smooth surface and the cart is moving with an acceleration of $3 \mathrm{~m} \mathrm{~s}^{-2}$ in the east direction. If another person $\mathrm{F}$ comes and starts pulling the cart with a force of $100 \mathrm{~N}$ due west, then the acceleration of the cart will be

A light spring balance hangs from the hook of the other light spring balance and a block of mass M kg hangs from the former one. Then the true statement about the scale reading is

One end of a long string of linear mass density $8.0 \times 10^{-3} \mathrm{~kg} \mathrm{~m}^{-1}$ is connected to an electrically driven tuning fork of frequency $256 \mathrm{~Hz}$, such that the frequency of tuning fork is equal to that of the string. The other end passes over a pulley and is tied to a pan containing a mass of $90 \mathrm{~kg}$. The pulley end absorbs all the incoming energy so that reflected waves at this end have negligible amplitude. At $t=0$, the left end (fork end) of the string $x=0$ has zero transverse displacement $(y=0)$ and is moving along positive $y$ direction. The amplitude of the wave is $5.0 \mathrm{~cm}$. Then the transverse displacement $y$ (in m) as function of $x$ and $t$ that describes the wave on the string. (Take $g=9.8 \mathrm{~m} / \mathrm{s}^2$ )

A man of mass $60 {~kg}$ climbed down using an elevator. The elevator had an acceleration of $4 {~ms}^{-2}$. If the acceleration due to gravity is $10 {~ms}^{-2}$, the man's apparent weight on his way down is

Law that proves that different masses accelerate to the earth at the same rate, but with different forces is

Swimming is possible on account of

Assertion : For the motion of electron around nucleus, Newton's second law is used.
Reason : Newton's second law can be used for motion of any object.

In an ideal string tension at all points of all string will be

Conservation of momentum in a collision between particles can be understood from

Which of the following sets of forces can not have resultant force equal to zero. (All forces are in newton).

The frictional force on a block of weight $10 \mathrm{~N}$ of area $0.1 \mathrm{~m}^2$ is $5 \mathrm{~N}$. If area of block is increased to $0.2 \mathrm{~m}^2$, keeping weight and material same; the frictional force on new block would be (assume all other conditions to be same)

A bullet of mass 28 grams is fired from a rifle of mass 11 kg with a velocity of 100 m/s. The recoil of the rifle is

The impulse on a particle due to a force acting on it during a given time interval is equal to the change in its

Statement-I: Angle of repose is equal to angle of limiting friction.
Statement-II: When the body is just at the point of motion, the force of friction in this stage is called as limiting friction.

A body of mass 60 kg is pushed with just enough force to start it moving on a rough surface with ${\mu _s} = 0.5$ and ${\mu _k} = 0.4$ and the force continues to act afterwards. The acceleration of the body is $\left( {\mathrm{in}\,m/{{\sec }^2}} \right)$

A body of mass 10 kg is moving on a horizontal surface by applying a force of 10 N in forward direction. If body moves with constant velocity, the work done by force of fiction for a displacement of 2m is

The laws of Newton's are applicable