Laws of motion practice · Medium

A particle is moving with a constant speed along a straight line path. A force is not required to

A spring balance and a physical balance are kept in a lift. In these balances equal masses are placed. If now the lift starts moving upwards with constant acceleration, then

Impulse is

Statement-1: A man is standing on a bathroom scale. Suddenly he squats (sits down) with acceleration $a$. The scale reading will increase.
Statement-2: Man pushes down on the scale while squatting.

Assertion $[A]$ : A boy feels more pain when he falls down on a hard concrete floor than when he falls on the sand floor

Reason $[R]$: Every action has equal and opposite reaction. The time of impact of cement floor is smaller compared to that of sand floor

Shock absorbers are used in vehicles to reduce the magnitude of

A block of weight 200 N is pulled along a rough horizontal surface at constant speed by a force of 100 N acting at an angle of ${30^0}$ above the horizontal. The force required to push the same block on the same surface making the same angle with the horizontal, to maintain the same constant speed will be

The two factors on which the momentum of a body depends are_____ and _____

It was calculated that a shell when fired from a gun with a certain velocity and at an angle of elevation $\frac{{5\mathrm{\pi }}}{{36}}$ rad should strike a given target. In actual practice, it was found that a hill just prevented the trajectory. At what angle of elevation should the gun be to hit the target?

A 5000 kg of rocket is set for firing. If the exhaust speed of gases is $1000\,\,m{s^{ - 1}}$ with respect to rocket, how much gas must be ejected each second to supply the thrust needed to overcome weight of the rocket?

A satellite in force-free space sweeps stationary interplanetary dust at a rate $dM/dt = \alpha v$ where M is the mass, v is the velocity of the satellite and α is a constant. What is the deacceleration of the satellite

External agencies like gravitational and magnetic forces ...X...
exerts force on a body from a distance.
Here, X refers to

When two blocks A and B coupled by a spring on a frictionless table are stretched and the released, then

For a body moving in a circular path, a condition for no skidding if $\mu$ is the coefficient of friction, is

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

Newton's second law of motion is

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

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

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

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

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.

When the speed of a moving body is doubled

Impulse of a force is equal to the change in-

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

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?