Laws of motion practice · Medium

If the net external force on a body is ...X..., its acceleration is zero. Acceleration can be ...Y... only, if there is a net external force on the body. Here, X and Y refer to

Starting from rest, the time taken by a body sliding down on a rough inclined plane at ${45^0}$ with the horizontal is twice the time taken to travel on a smooth plane of same inclination and same distance. Then the coefficient of kinetic friction is

What is the working principle of a jet engine?

Statement-I: The work done in bringing a body down from the top to the base along a frictionless incline plane is the same as the work done in bringing it down the vertical side
Statement-II: The gravitational force on the body along the inclined plane is the same as that along the vertical side.

Impulse of a force is equal to the change in-

A 60 kg man stands on a spring scale in the lift. At some instant he finds, scale reading has changed from 60 kg to 50 kg for a while and then comes back to the original mark. What should we conclude

An open carriage in a goods train is moving with a uniform velocity of 10 $\;\mathrm{m}{\mathrm{s}^{ - 1}}$. If the rain adds water with zero velocity at the rate of 5 $\mathrm{kg}{\mathrm{s}^{ - 1}}$, then the additional force applied by the engine to maintain the same velocity of the train is

A particle of mass 10g is moving with a velocity $2\hat i + \hat j + 3\hat k$ (cm/s) Magnitude of its linear momentum is

Statement-I: The velocity of a body at the bottom of an incline plane of given height is more when it slides down the plane, compared to, when it rolling down the same plane.
Statement-II: In rolling down a body acquires both, kinetic energy of translation and rotation.

Statement-1: For a body resting on level ground normal reaction and weight form Newton's $3^{\text {rd}}$ law action-reaction pair.
Statement-2: Action-reaction pair of Newton's $3^{\text {rd}}$ law are equal and opposite.

If a force of 200 N acts on a body, the momentum acquired is $150\,\,{\text{kg}}\,\,{\text{m}}{{\text{s}}^{ - 1}}.$ The period for which the force acts on the body (in sec) is

A gun when firing bullet recoils, this can be explained by

In a TV picture tube electrons are ejected from the cathode with negligible speed and reach a velocity of $5 \times 10^6 \mathrm{~m} / \mathrm{s}$ in travelling one centimeter. Assuming straight line motion, find the constant force exerted on the electron. The mass of the electron is $9.1 \times 10^{-31} \mathrm{~kg}$.

Assertion: If there is an isolated system of particle exists, then its total momentum is conserved.
Reason: The law of conservation of momentum follows from the second and third law of motion.

A block is given certain upward velocity along the incline of elevation $\alpha$. The time of ascent to upper point was found to be half the time of descent to initial point. The co-efficient of friction between block and incline is:

Bullets of $0.03 \mathrm{~kg}$ mass each hit a plate at the rate of 200 bullets per second, with a velocity of $50 \mathrm{~m} / \mathrm{s}$ and reflect back with a velocity of $30 \mathrm{~ms}^{-1}$. The average force acting on the plate in Newton is

An object at rest in space suddenly explodes into three parts of same mass. The momentum of the two parts are $2p\hat i\,and\,p\hat j$. The momentum of the third part

A block is placed at distance of 2 m from the rear on the floor of a truck $\left( {g = 10\,m{s^{ - 2}}} \right).$ When the truck moves with an acceleration of $8\,m{s^{ - 2}},$ the block takes 2 sec to fall off from the rear of the truck. The coefficient of sliding friction between truck and the block is

A truck starts from rest and has acceleration of $4 \mathrm{~m} \mathrm{~s}^{-2}$. A box is inside truck which is at $6 \mathrm{~m}$ from open end of truck. The coefficient of friction between box and truck is $0.1.$ How much time box will take to slip out of truck?

If the maximum possible exhaust velocity of a rocket be $2 \mathrm{~kms}^{-1}$, calculate the ratio $m_0 / m$ for it if it is to acquire the escape velocity of $11.2 \mathrm{~kms}^{-1}$ after starting from rest.

The minimum velocity $\left( {\mathrm{in\;m}{\mathrm{s}^{ - 1}}} \right)$ with which a car driver must traverse a flat curve of radius of 150 m and coefficient of friction 0.6 to avoid skidding is

A body is acted upon by balanced forces,

Observer ${O_1}$ is in a lift going upwards and ${O_2}$ is on the ground. Both apply Newton’s law, and measure normal reaction on the body

Aeroplanes are streamlined to reduce

Assertion: When a person walks on a rough surface, the frictional force exerted by the surface on the person is opposite to the direction of the tendency of motion of his legs.
Reason: If a body moves with constant velocity, it implies that it is moving along a straight line and there is no acceleration.

A force produces an acceleration of 1 m/s in a body of mass 1 kg. This form is defined as?

A body of mass $m$ moves along $X$-axis such that its position co-ordinate at any instant $t$ is $x=at^4-bt^3+ct$, where $a, b$ and $c$ are constants. What is the force acting on the particle at any instant $t$?

A car of mass 800 kg moves on a circular track of radius 40 m. If the coefficient of friction is 0.5, then maximum velocity with which the car can move is

A woman of $50 \mathrm{~kg}$ mass is standing in an elevator.
Suddenly, the cable of the elevator breaks and the elevator begins to fall freely. The force exerted by the floor of the elevator on the woman is

A block is placed on a rough horizontal floor and a horizontal force $F$ is applied on it. The force of friction $f$ by the floor on the block is measured for different values of $F$ and a graph is plotted between them. Then the graph will be a