Laws of motion practice · Mixed difficulty

A block of mass $m=11.7 \mathrm{~kg}$ is to be pushed a distance of $s=4.65 \mathrm{~m}$ along an incline and raised to a distance of $h=2.86 \mathrm{~m}$. Assuming frictionless surface, calculate the work done in applying a force parallel to the incline to push the block up at a constant speed. (Take, $g=9.8 \mathrm{~ms}^{-2}$ )

A person is standing in an elevator. In which situation, he experiences weight loss?

An air tight cage in which a bird is sitting is suspended from a spring balance. If the bird starts flying, then the reading of the balance will

A car is moving on a circular level road of radius of curvature 300 m. If the coefficient of friction is 0.3 and acceleration due to gravity $10\;\mathrm{m}{\mathrm{s}^{ - 2}}$, the maximum speed the car can have is (in km ${\mathrm{h}^{ - 1}}$)

Assertion: Frictional forces are conservating forces.
Reason: Potential energy can be associated with frictional forces.

Which of the following statement/s is/are correct?

Statement I: Work done by kinetic friction in a closed path is not zero.

Statement II: Kinetic frictional force is a nonconservative force.

The coefficients of static and dynamic friction are 0.7 and 0.4. The minimum force required to create motion is applied on a body and if it is further continued, the acceleration attained by the body in $m{s^{ - 2}}$ is $(g = 10\,m/{s^2})$

The force of friction and tension in a string are derived from

Sand drops fall vertically at the rate of $2 \mathrm{~kg} / \mathrm{sec}$ on to a conveyor belt moving horizontally with the velocity of $0.2 \mathrm{~m} / \mathrm{sec}$. Then the extra force needed to keep the belt moving is

Assertion: Static friction is self adjusting but kinetic friction is a constant force for a certain range of speed.
Reason: A body slides down an inclined plane if the angle of friction is more than the angle of the inclined plane with the horizontal.

Two blocks of equal mass $m$ are connected by an
unstretched spring and the system is kept at rest on a
frictionless horizontal surface. A constant force $F$ is
applied on one of the blocks pulling it away from the
other as shown in figure.
(a) Find the position of
the centre of mass at time $t.$
(b) If the extension of the spring is $x_0$
at time $t,$ find the displacement of the two
blocks at this instant.

A body of 5 kg is moving with a velocity of 20m/s. If a force of 100N is applied on it for 10s in the same direction as its velocity, what will now be the velocity of the body

Which one of the following is not a force

To the free end of spring hanging from a rigid support, a block of mass m is hung and slowly allowed to come to its equilibrium position. Then stretching in the spring is d. if the same block is attached to the same spring and allowed to fall suddenly, the amount of stretching is (force constant ,k)

A student unable to answer a question on Newton’s law of motion attempts to pull himself up by tugging on his hair. He will not succeed

The coefficients of static and dynamic friction are 0.7 and 0.4. The minimum force required to create motion is applied on a body and if it is further continued, the acceleration attained by the body in $m{s^{ - 2}}$ is $(g = 10\,m/{s^2})$

A stationary particle breaks into two parts of masses $\mathrm{m}_{\mathrm{A}}$ and $\mathrm{m}_{\mathrm{B}}$ which move with velocities $\mathrm{v}_{\mathrm{A}}$ and $\mathrm{v}_{\mathrm{B}}$ respectively. The ratio of their kinetic energies $\left(\mathrm{K}_{\mathrm{B}}: \mathrm{K}_{\mathrm{A}}\right)$ is :

One feels heavier in a lift when the lift

When a bus of mass $1000 \mathrm{~kg}$ is moving with a velocity of $20 \mathrm{~ms}^{-1}$ on a rough horizontal road, surface its engine is switched off then, how far does the bus move before it comes to rest (velocity $=0$ ) if the coefficient of kinetic friction between the road surface and tyres of the bus is 0.75 ?

A box of mass m kg is placed on the rear side of an open truck accelerating at $t\;\mathrm{m}{\mathrm{s}^{ - 2}}$. The coefficient of friction between the box and the surface below it is 0.4. The net acceleration of the box with respect to the truck is zero. The value of m is [Given $\mathrm{g} = 10\mathrm{\;m}{\mathrm{s}^{ - 2}}$)

A golf ball of mass $50 \,{gm}$ placed on a tee, is truck by a golf-club. The speed of the golf ball as it leaves the tee is $100 {~m} / {s}$, the time of contact on the ball is $0.02 {~s}$. If the force decreases to zero linearly with time, then the force at the beginning of the contact is

A lift is moving upwards with a uniform velocity v in which a block of mass m is lying. The frictional force offered by the block, when coefficient of the frictional is $\mu$, will be

Assertion : A cyclist always bends inwards while negotiating a curve.
Reason : By bending, cyclist lowers his centre of gravity.

When a particle moves in a circle with a uniform speed

Assertion: Animate object can accelerate in the absence of external force.

Reason: Newton's second law is not applicable on animate object.

If a force of 260 N acts on a body the momentum required is 126 kg m/s. The period for which the force acts on the body is

A motorcyclist wants to drive on the vertical surface of wooden 'well' of radius $5 \mathrm{~m}$, with a minimum speed of $5 \sqrt{5} \mathrm{~ms}^{-1}$. The minimum value of coefficient of friction between the tyres and the wall of the well must be (Take, $g=10 \mathrm{~ms}^{-2}$)

In case of horse pulling a cart, the force that causes the horse to move forward is the force that

A car moves at a speed of $20 \mathrm{~ms}^{-1}$ on a banked track and describes an arc of a circle of radius $40 \sqrt{3} \mathrm{~m}$. The angle of banking is $\left(\mathrm{g}=10 \mathrm{~ms}^{-2}\right)$

A lift of mass $1000 \mathrm{~kg}$ which is moving with acceleration of $1 \mathrm{~m} / \mathrm{s}^2$ in upward direction, then the tension developed in string which is connected to lift is