Laws of motion practice · Easy

Assertion: During head on collision between two bodies let $\Delta p_1$ is change in momentum of first body and $\Delta p_2$ the change in momentum of the other body, then $\Delta p_1=\Delta p_2$.

Reason: Total momentum of the system should remain constant.

Three forces are acting on a body to make it in equilibrium, which set can not do it?

A block of mass $100 {~kg}$ slides over a distance of $10 {~m}$ on a horizontal surface. If the co-efficient of friction between the surface is 0.4, then the work done against friction (in $J$) is:

An object is placed on the surface of a smooth inclined plane of inclination $\theta$. It takes time $t$ to reach the bottom of the inclined plane. If the same object is allowed to slide down rough inclined plane of same inclination $\theta$, it takes time nt to reach the bottom where $\mathrm{n}$ is a number greater than 1 . The coefficient of friction $\mu$ is given by

Which of the following statement (s) is/are incorrect?

A particle of mass $m$ travelling along $x$-axis with speed $v_0$ shoots out $1 / 3^{\text {rd}}$ of its mass with a speed $2 v_0$ along $y$-axis. The velocity of remaining piece is:

Three blocks A, B and C of masses $3 \mathrm{~kg}, 2 \mathrm{~kg}$ and $1 \mathrm{~kg}$ respectively connected by two ideal strings are present on a smooth horizontal surface. An external horizontal force of $18 \mathrm{~N}$ acts on the block A to pull the system. Find the difference in the tensions in strings connecting A $\&$ B and, B $\&$ C (in Newton).

A body of mass 10 kg is moving with a uniform velocity $100\,cm{s^{ - 1}}.$ The force required to stop the vehicle in 10 s is

Assertion(A): Even though net external force on a body is zero, momentum need not to conserved.

Reason(R): The internal interaction between particles of a body cancels out momentum of each other.

Assertion: If the magnitude of net external force on a body is zero, its acceleration will be zero.
Reason: The given statement is the also a form of Newton’s second law of motion.

A block of mass 2 kg rests on a rough inclined plane making an angle of $30^\circ$ with the horizontal. If ${\mu _S} = 0.6$, what is the frictional force on the block?

Which one of the following is not a contact force?

A body of mass $2 \mathrm{~kg}$ begins to move under the action of a time dependent force given by $\vec{F}=\left(6 t \hat{i}+6 t^2 \hat{j}\right) N$. The power developed by the force at the time $t$ is given by

When a ball is whirled in a circle and the string supporting the ball is released, the ball flies off tangentially. This is due to

A large force is acting on a body for a short time. The impulsive imparted is equal to the change in

A particle of mass $m$ is moving with a uniform velocity $v_1$. It is given an impulse such that its velocity becomes $v_2$. The impulse is equal to

An object is moving on a plane surface with uniform velocity $10 \mathrm{~ms}^{-1}$ in presence of a force $10 \mathrm{~N}$. The frictional force between the object and the surface is

A good lubricant should be highly

A gun of mass 10 kg fires four bullet per second. The mass of each bullet is 20 g and the velocity of the bullet when it leaves the gun is $300\,m{s^{ - 1}}.$ The force required to hold the gun while firing is

A block of mass 4 kg rests on a rough inclined plane making an angle of $45^\circ$ with the horizontal, if ${\mu _s} = 0.5$ The frictional force on the block is

Assertion: To conserve linear momentum of a system, no force should act on the system.

Reason: If net force on a system is zero, its linear momentum should remain constant.

The force of kinetic friction does not depend on

A rider on horse falls backward when horse starts running all of a sudden because of

A body is projected up a $45^{\circ}$ rough incline. If the coefficient of friction is 0.5 , then the retardation of the block is

Two bodies of masses 4 kg and 16 kg at rest to acted upon by same force. The ratio of times required to attain the same speed is

The propulsion of a rocket is based on the principle of conservation of

A body of mass M collides against a wall with a velocity V and retraces its path with the same speed. The change in momentum is [take initial direction of velocity as positive]

A wooden block of 90 kg is about to be pushed on a floor of coefficient of friction 0.3. The magnitude of the force of friction on the wooden block when it is just pushed is $\left( {g = 10\,m/{s^2}} \right).$

A brick of mass 3 kg just begins to side down on inclined plane at an angle of $60^\circ$ with the horizontal. The force of friction will be

A block of mass 1 kg slides down on a rough inclined plane of inclination 60° starting from its top. If the coefficient of kinetic friction is 0.5 and length of the plane is 1 m, then work done against friction is (Take $g = 9.8\;m/{s^2}$)