Laws of motion practice · Medium

The breaking strength of the cable used to pull a body is $40 \mathrm{~N}$. A body of mass $8 \mathrm{~kg}$ is resting on a table of coefficient of friction $\mu=0.2$ The maximum acceleration which can be peoduced by the cable connected to the body is (Take, $g=10 \mathrm{~ms}^{-2}$)

A stick of 1 m is moving with velocity of $2.7 \times {10^8}\;m{s^{ - 1}}$. What is the apparent length of the stick $\left( {c = 3 \times {{10}^8}\;m{s^{ - 1}}} \right)$

A cyclist is speeding at $20 \mathrm{~m} / \mathrm{s}$ on a level road taking a level circular turn of radius $200 \mathrm{~m}$ without reducing speed. What is minimum coefficient of static friction required between tyres and road so that cyclist take turn without slipping?

A trolley filled with sand moves on a smooth horizontal surface with a velocity ${V}_{{0}}$. A small hole is made at the base of it from which sand is leaking out vertically down at constant rate. As the sand leaks out
a) The velocity of the trolley remains constant
b) The velocity of the trolley increases
c) The velocity of trolley decreases
d) The momentum of trolley + leaked out sand is conserved

(A): A sphere cannot roll on a smooth inclined surface.
(R): For a smooth inclined surface force of friction is equal to zero.

A bullet hits and gets embedded in a solid block resting on a frictionless surface .In this process which one of the following is correct?

Assertion: Static friction is a force which can be self-adjusted up to its limit $\mu_{{s}} {N}$ where $\mu_{{s}}$ is the co-efficient of static friction.
Reason: The equation $f_s=\mu_s N$ is applicable only when the maximum value of static friction comes into play.

Which of the following statements is/are correct about action and reaction forces?
I. Action and reaction are simultancous forces
II. There is no cause-effect relation between action and reaction.
III. Action and reaction always on two different body

A rectangular wooden box $10 \mathrm{~cm} \times 20 \mathrm{~cm} \times 40 \mathrm{~cm}$ in size is kept on a horizontal surface with its face of largest area on the surface. A minimum force of $10 \mathrm{~N}$ applied parallel to the surface sets the box in sliding motion along the surface. If the box is now kept with its face of smaller area in contact with the surface, the minimum force applied parallel to the surface, to set the box in motion, is

The coefficient of static friction between two surfaces depends upon

A block has been placed on an inclined plane with the slope
angle $\theta,$ block slides down the plane at constant speed. The
coefficient of kinetic friction is equal to

A sphere cannot roll without applying external force on

Three concurrent co-planar forces 1 N,2 N and 3 N acting along different directions on a body

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

1 kg body explodes into three fragments. The ratio of their masses is $1:1:3$. The fragments of same mass move perpendicular to each other with speeds $\;30\mathrm{m}{\mathrm{s}^{ - 1}}$, while the heavier part remains in the initial direction. The speed of heavier part is

Tension in the cable supporting an elevator, is equal to the weight of the elevator. From this, we can conclude that the elevator is going up or down with a

When the speed of a moving body is doubled

Statement-I: Shock absorbers reduce the magnitude of change in momentum.
Statement-II: Shock absorbers increase the time of action of impulsive force.

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 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