Laws of motion practice · Mixed difficulty

For a body moving with relativistic speed, if the velocity is doubled then

Newton's second law of motion is

The change in momentum per unit time of a body represents

If ${\mu _r},\,\,{\mu _k}$ and ${\mu _s}$ represent the coefficients of rolling friction, kinetic and static friction, then

If the coefficient of friction is $\sqrt 3 ,$ the angle of friction is

A person is measuring his weight by standing on a weighing machine inside a lift. When the lift is at rest, the machine shows his weight to be 55 kg. In between the floor when the lift is moving up with a constant speed of 10 km/hr, he again measures his weight, which is

The three central concepts in Newtonian mechanics are

A body of mass $40 \mathrm{~kg}$ resting on rough horizontal surface is subjected to a force $P$ which is just enough to start the motion of the body. If $\mu_s=0.5$, $\mu_k=0.4, g=10 \mathrm{~ms}^{-2}$ and the force $P$ is continuously applied on the body, then the acceleration of the body is

The average resisting force that must act on a 6 kg mass to reduce its speed from 65 cm/s to 15 cm/s in 0.3 s is

Statement-1: A man starts walking towards west. Friction force on him acts towards east.
Statement-2 : Friction opposes relative motion.

Statement I: A car is moving in a horizontal circular plane with varying speed, then the frictional force is neither pointing towards the radial direction nor along the tangential direction.
Statement II: Components of the frictional force are providing the necessary tangential and centripetal acceleration, in the above situation.

A block moves down a smooth inclined plane of inclination $\theta$. Its velocity on reaching the bottom is v. If it slides down a rough inclined plane of same inclination, its velocity on reaching the bottom is v/n, where n is a number greater than 1. The coefficient of friction is given by

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

A block of mass 3 kg is placed on the floor. The coefficient of static friction is 0.6. If a force of 3.8 N is applied on the block parallel to the floor, the force of friction between the block and floor $\left( {g = 10\,m/{s^2}} \right)$ is

Assertion: The apparent weight of a person standing in a lift which moves upwards with uniform acceleration is always higher than his true weight.
Reason: The weight (on the earth surface) always acts downwards.

A block is limiting equilibrium on a rough horizontal surface. If the net contact force is $\sqrt 3$ times the normal force, the coefficient of static friction is

When the speed of a moving body is doubled

Impulse of a force is equal to the change in-

A dynamometer $D$ is attached to two bodies of masses $M=6 \mathrm{~kg}$ and $m=4 \mathrm{~kg}$. Forces $F=20 \mathrm{~N}$ and $f=10 \mathrm{~N}$ are applied to the masses as shown. The dynamometer reads

A body of mass 0.5 kg is projected under gravity with a speed of 98 m/s at an angle of ${30^0}$ with the horizontal. The change in momentum (in magnitude) of the body is

In the above ques., the height to which the lift takes the passenger is

It is easier to draw up a wooden block along an inclined plane than to haul it vertically, principally because

STATEMENT-1 : It is easier to pull a heavy object than to push it on a level ground and

STATEMENT-2 : The magnitude of frictional force depends on the nature of the two surfaces in contact.

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 body of mass 500g is thrown upwards with a velocity 20 m/s. It momentarily comes to rest after attaining height of 16m. How much energy is lost due to air friction?

When an elevator is moving downward with a increasing speed, the apparent weight of a body inside elevator

The apparent weight of a mass in a lift moving up is 80 kg when its weight in the stationary lift is 60 kg. If the same lift now moves up with same retardation the weight of the mass will be

A force of $10 \mathrm{~N}$ acts on a body of mass $0.5 \mathrm{~kg}$ for 0.25 s starting from rest. What is its impulse?

A projectile of mass m is thrown with a velocity v making an angle of ${45^0}$ with the horizontal. The change in momentum from departure to arrival along vertical direction, is

If the normal force is doubled, the coefficient of friction is