Laws of motion practice · Medium

Which of the following is NOT a fundamental force in nature?

A body starts sliding down an inclined plane of inclination $30^{\circ}$. The upper part of length $2 {~m}$ is smooth and lower part of length $4 {~m}$ is rough. The coefficient of friction between the plane and the body, if the body is brought to rest just when it reaches the bottom

On a banked road, which force is essential to provide the necessary centripetal force to a car to take a turn while driving at the optimum speed?

Which one of the following is not used to reduce friction

A vehicle of mass 120 kg is moving with a uniform velocity of 108 $\;\mathrm{km}{\mathrm{h}^{ - 1}}$. The force required to step the vehicle in 10 s is

An object of mass $3 {~kg}$ is at rest. Now a force of $\vec{F}=6 t^2 \hat{i}+4 t \hat{j}$ is applied on the object then the velocity of the object at $t=3 {~s}$ is

The object at rest suddenly explodes into three parts with the mass ratio 2:1:1. The parts of equal masses move at right angles to each other with equal speed ‘$v$’. The speed of the third part after explosion will be

Human heart is pumping blood with constant velocity $v\,m\,{s^{ - 1}}$ at the rate of $M\,kg\,{s^{ - 1}}.$ The force required for this is (in $N$)

Assertion: The weighing machine measures the weight of a body.
Reason: Weightlessness means the absence of weight.

In a non-inertial frame, the second law of motion is written as
where, $\mathbf{F}_p$ is pseudo force while $\mathbf{a}$ is the acceleration of the body relative to the non-inertial frame.

A machine gun fires a bullet of 10 g with a speed of $100\,m{s^{ - 1}}.$ A person holding the gun can exert a maximum force of 100 N on it. The number of bullets that can be fired from the gun per second is

A force vector applied on a mass is represented as $\vec{F}=(6 \hat{i}-8 \hat{j}+10 \hat{k}) \mathrm{N}$ and accelerates with $1 \mathrm{~m} / \mathrm{sec}^2$. What will be the mass of the body?

If a person with a spring balance and a body hanging from it goes up and up in an aeroplane, then the reading of the weight of the body as indicated by the spring balance will

A rocket of initial mass $6,000 \mathrm{~kg}$ ejects mass at a constant rate of $16 \mathrm{~kg} \mathrm{~s}^{-1}$ with constant relative speed of $11 \mathrm{kms}^{-1}$. What is acceleration of the rocket a minute after the blast? Neglect gravity.

At a certain instant of time the mass of rocket going up vertically is 100 kg. If it is ejecting 5 kg of gas per second at a speed of 400 m/s, the acceleration of the rocket would be (Taking $g = 10\;\mathrm{m}/{\mathrm{s}^2})$

A minimum force $F$ is applied to a block of mass $102 \mathrm{~kg}$ to prevent it from sliding on a plane with an inclination angle $30^{\circ}$ with the horizontal. If the coefficients of static and kinetic friction between the block and the plane are $0.4$ and $0.3$ respectively, then the force $F$ is

An object of mass $15 {~kg}$ moves at a constant speed of $15 {~ms}^{-1}$. A constant force, which acts for 5 seconds on the object gives it a speed 5 ${ms}^{-1}$ in opposite direction. The force acting on the object is?

Assertion: Rocket in flight is not an illustration of projectile.

Reason: Rocket takes flight due to combustion of fuel and does not move under the gravity effect alone

When a train takes a turn, the passengers are thrown outwards because of-

Units of impulse is

A body under the action of a force $\bar F = 9i - 6j + 8k$ acquires an acceleration of $2\,\,m/{s^2}.$ The mass of this body be

A book of weight 20 N is pressed between two hands and each hand exerts a force of 40 N. If the book just starts to slide down. Coefficient of friction is

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

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

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