Laws of motion practice · Medium

A $4 \mathrm{~kg}$ block is suspended from the ceiling of an elevator through a spring having a linear mass density of $19.2 \times 10^{-3} \mathrm{kgm}^{-3}$ Find the speed with respect to spring with which a wave pulse can proceed on the Spring if the elevator accelerates up at the rate of $2.0 \mathrm{~ms}^{-2}$ take $g=10 \mathrm{~ms}^{-2}$

Statement-I: When a ball of mass $m$ hits normally a wall with a velocity '$v$' and rebounds with same velocity $v$, impulse imparted to the wall is $2 m v$.
Statement-II: Impulse $=$ change in linear momentum

Select correct statement regarding friction

Impulse equals

A force of 40 newton acts on a body which is initially at rest. If the velocity of the body at the end of 10 seconds is $20\,\,\,{\text{m}}{{\text{s}}^{ - 1}},$ then mass of the body

If two masses (M & m) are connected on a horizontal plane and a force is applied on the combination, then the tension T depends on

The coefficient of friction between the tyres and the road is 0.25. The maximum speed with which a car can be driven round a curve a radius 40 m without skidding is is (assume $g = 10\;m{s^{ - 2}}$)

A cold soft drink is kept on the balance. When the cap is open, then the weight

A frictionless inclined plane of length l having inclination &theta; is placed inside a lift which is accelerating downward with an acceleration a($<g$) .&nbsp;If a block is allowed to move, down the inclined plane, from rest, then the time taken by the block to slide from top of the inclined plane to the bottom of the inclined plane is

No force is required for

An ice cart of mass 60 kg rests on a horizontal snow patch with coefficient of static friction $\frac{1}{3}$. Assuming that there is no vertical acceleration, find the magnitude of the maximum horizontal force required to move the ice cart $\left( {g = 9.8\;\mathrm{m}{\mathrm{s}^{ - 2}}} \right)$

A shell is fired with a muzzle velocity of $20\,m{s^{ - 1}}$ at an angle of ${60^0}$ with the horizontal. At the top of trajectory the shell explodes into 2 fragments of equal masses. One of them comes to rest. The distance at which second fragment touches the ground from gun will be…. $\left( {g = 10\,m/{s^2}} \right)$

A cubical block of mass $M$ vibrates horizontally with amplitude of $4 \mathrm{~cm}$ and a frequency of $2 \mathrm{~Hz}$. A small block of mass $m$ is placed on the bigger block. In order that the smaller block does not slide on the bigger block, the minimum value of the coefficient of static friction between the two blocks is

A gun is mounted on a railroad car. The mass of the car, the gun, the shells and the operator is $50 \mathrm{~m}$ where $m$ is the mass of one shell. If the velocity of the shell with respect to the gun (in its state before firing) is $200 \mathrm{~m} / \mathrm{s},$ what is the recoil speed of the car after the second shot? Neglect friction.

Which of the following is a self adjusting force?

Physical independence of force is a consequence of

The x and y components of a force are 2 N and -3N. The force is

Assertion: A sphere cannot roll on a frictionless horizontal surface.
Reason: The tangential frictional force on the sphere exerts torque and causes it to roll.

A man squatting on the ground gets straight up and stand. The force of reaction of ground on the man during the process is

Identify the correct statement.

Assertion: The acceleration of a body down a rough inclined plane is greater than the acceleration due to gravity.
Reason: A body is able to slide on an inclined plane only when its acceleration is greater than the acceleration due to gravity.

An object is moving at constant velocity. The total force $F$ acting on the object is given by

Inertia of an object is directly dependent on

Assertion: A cricketer moves his hands forward to catch a ball so as to catch it easily without hurting.
Reason: He tries to decrease the distance travelled by the ball so that it hurts less.

A bullet of mass $0.04 {~kg}$ moving with a speed of $90 {~ms}^{-1}$ enters a having wooden block and is stopped after a distance of $60 {~cm}$. The average resistive force exerted by the block on the bullet is

STATEMENT-1 : A block of mass $m$ starts moving on a rough horizontal surface with a velocity $v$. It stops due to friction between the block and the surface after moving through a certain distance. The surface is now tilted to an angle of $30^{\circ}$ with the horizontal and the same block is made to go up on the surface with the same initial velocity $v$. The decrease in the mechanical energy in the second situation is smaller than that in the first situation.

STATEMENT-2 : The coefficient of friction between the block and the surface decreases with the increase in the angle of inclination.

In a legend the hero-kid kicked a toy pig so that it is projected with a speed greater than that of its cry. If the weight of the toy pig is assumed to be 5 kg and the time of contact 0.01 s, the force with which the hero-kid kicked him was (Speed of cry = 330 m/s)

A car is moving with a uniform speed on a level road. Inside the car there is a balloon filled with helium and attached to a piece of string tied to the floor. The string is observed to be vertical. The car now takes a left turn maintaining the speed on the level road. The balloon in the car will (Here the car is supposed to be air tight)

Assertion: Impulsive force is large and acts for a short time.

Reason: Finite change in momentum should be produced by the force.

Body A is placed on frictionless wedge making an angle $\theta$ with the horizon. The horizontal acceleration towards left to be imparted to the wedge for the body A to freely fall vertically, is