Laws of motion practice · Medium

A hammer of mass $10 \mathrm{~kg}$ moving with a speed of $5 \mathrm{~m} / \mathrm{s}$ strikes the head of a nail driving it $30 \mathrm{~cm}$ into the wall. Find the impulse imparted to the nail.

A body of mass 60 kg is pushed with just enough force to start it moving on a rough surface with ${\mu _s} = 0.5$ and ${\mu _k} = 0.4$ and the force continues to act afterwards. The acceleration of the body is $\left( {\mathrm{in}\,m/{{\sec }^2}} \right)$

A rocket motor consumes $100 \mathrm{~kg}$ of fuel per second, exhausting it with a speed of $5 \times 10^3 \mathrm{~ms}^{-1}$. What force is exerted on the rocket?

Assertion: A table cloth can be pulled from a table without dislodging the table.
Reason: For a moving object, if its speed changes, its velocity must change and it must have some acceleration.

Three weights $\mathrm{W}, 2 \mathrm{~W}$ and $3 \mathrm{~W}$ are connected to identical springs suspended from rigid horizontal rod. The assembly of the rod and the weights fall freely. The positions of the weights from the rod are such that

Select the incorrect statement(s) from the following.
I. Limiting friction is always greater than the kinetic friction
II. Limiting friction is always less than the static friction
III. Coefficient of static fiction is always greater than the coefficient of kinetic fiction

A bullet of mass $20 {~g}$ moving with a speed of $100 {~m} {~s}^{-1}$ enters a heavy wooden block and stops after a distance of $50 {~cm}$. The average resistive force exerted by the block on the bullet is

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

A lift is descending with a constant velocity ' ${v}$ '. A man in the lift drops a coin. The coin experiences an acceleration towards the floor equal to :

Formula for true force is

Assertion: Frictional force opposes relative motion and dissipates power in the form of heat.
Reason: Friction is always an undesirable force.

When an elevator cabin falls down, the cabin and all the bodies fixed in the cabin are accelerated with respect to

If a stone is thrown out of an accelerated train, then
acceleration of the stone at any instant depends on

Statement I: A cloth covers a table. Some dishes are kept on it. The cloth can be pulled out without dislodging the dishes from the table.
Statement II: For every action there is an equal and opposite reaction.

A platform is moving upwards with an acceleration of $5 \mathrm{~ms}^{-2}$. At the moment when its velocity is $u=3 \mathrm{~ms}^{-1}$, a ball is thrown from it with a speed of $30 \mathrm{~ms}^{-1}$ w.r.t. platform at an angle of $\theta=30^{\circ}$ with horizontal. The time taken by the ball to return to the platform is

Statement I: If bodies slide down an inclined plane without rolling, then all the bodies reach the bottom simultaneously.

Statement II: Acceleration of all bodies are equal and independent of shape.

A body of mass $10 {~kg}$ is acted upon by a force given by equation $F=\left(3 t^2-30\right)$ Newton's, The initial velocity of the body is $10 {~m} / {s}$. The velocity of the body after $5 {sec}$ is

A spacecraft of mass M is moving with velocity v in free space when it explodes and breaks in two. After the explosion, a mass m of the spacecraft is left stationary. What is the velocity of other part?

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

The net force acting is not zero on

An athlete does not come to rest immediately after crossing the winning line due to the

Two equals forces are acting at a point with an angle of $60^{\circ}$ between them. If the resultant force is equal to $40 \sqrt{3} \mathrm{~N}$, the magnitude of each force is

A body of mass $m$ is launched up on a rough inclined plane making an angle $45^{\circ}$ with horizontal. If the time of ascent is half of the time of descent, the frictional coefficient between plane and body is

Statement-I: Newton's third law of motion is applicable only when bodies are in motion or rest.
Statement-II: Newton's third law applies to all types of force, e.g. gravitational, electric or magnetic forces etc.

Assertion: When a force $\vec{F}$ attempts to slide a body along a surface, a frictional force parallel to the surface and directed so as to oppose the sliding, is exerted on the body by the surface.
Reason: It is due to the bonding between the body and the surface.

Assertion : The two bodies of masses M and m (M > m) are allowed to fall from the same height if the air resistance for each be the same then both the bodies will reach the earth simultaneously.
Reason : For same air resistance, acceleration of both the bodies will be same.

A body of mass 10 kg is projected from the ground with a velocity 30 m/s at an angle $60^\circ$ with the vertical. If ${t_1}$ is the time in seconds at which the body is projected and ${t_2}$ is the time in seconds at which reaches the ground. The change in momentum in $kgm{s^{ - 1}}$ during the time $\left( {{t_2} - {t_1}} \right)$ is

Statement-I: A concept of pseudo forces is valid both for inertial as well as non-inertial frame of reference
Statement-II: A frame accelerated with respect to an inertial frame is a non-inertial frame.

A lift of mass $2000 \mathrm{~kg}$ is supported by thick steel ropes. If maximum upward acceleration of the lift be $1.2 \mathrm{~ms}^{-2}$, and the breaking stress for the ropes be $2.8 \times 10^8 \mathrm{~Nm}^{-2}$, what should be the minimum diameter of rope?

Statement-I: If the force varies with time in a complicated way then the net force is measured by the total change in momentum of the body.
Statement-II: Change in momentum and impulsive force are numerically equal.