Work-energy-power practice · Medium

A particle is moving along a circular path with a uniform speed. How does its angular velocity change when it completes half of the circular path?

A bullet of mass $m$ moving with a horizontal velocity $u$ strikes a stationary wooden block of mass $M$ suspended by a string of length $L=50 \mathrm{~cm}$. The bullet emerges out of the block with speed $\frac{u}{4}$. If $M=6 \mathrm{~m}$, the minimum value of $u$, so that the block can complete the vertical circle, is (Take, $g=10 \mathrm{~ms}^{-2}$ )

A bullet of mass m moving with velocity v strikes a suspended wooden block of mass M. If the block rises to a height h, the initial velocity of the block will be

A car is moving on a circular path and takes a turn. If ${R_1}\,and\,{R_2}$ be the reactions on the inner and outer wheels respectively, then

Assertion: A spring has potential energy, when it is either compressed or stretched.
Reason: In compressing or stretching a spring, work is done on it against the restoring force.

The angular acceleration of a body, moving along the circumference of a circle, is

A ball of mass $m_1$ collides head-on and elastically with an identical ball of mass $m_2$, initially at rest. The transfer of energy will be maximum when

A particle moves along a circle with a uniform speed $\mathrm{v}$. After it has made an angle of $60^{\circ}$ its speed will be

Assertion: If a particle moves along circular path with constant speed then acceleration must be present.
Reason: If a particle moves with variable velocity then acceleration must be present.

The work done by the gravity on a body moving upwards is

The kinetic energy in water is used to

When a man increases his speed by $2\;\mathrm{m}{\mathrm{s}^{ - 1}}$, he finds that his kinetic energy is doubled, the original speed of the man is

A body of mass 4 kg is moving with momentum of $8\mathrm{\;kg} - \mathrm{m}{\mathrm{s}^{ - 1}}$. A force of 0.2 N acts on it in the direction of motion of the body for 10 s. The increase in KE in joule is

1. During any collision, velocity along common tangent doesn’t change.
2. In an elastic collision with equal masses, the velocity along common normal is interchanged.
3. When a ball makes an oblique inelastic collision with a fixed target the reflection angle is less than incidence.
4. In a one dimensional elastic collision the fraction of kinetic energy transferred by a projectile to a stationary target is $\frac{4 m_1 m_2}{\left(m_1+m_2\right)^2}$.

An object of mass $m_1=2 \mathrm{~kg}$, moving with velocity $v_{i1}=12 \mathrm{~m} / \mathrm{s}$, collides head-on with a stationary object whose mass is $m_2=6 \mathrm{~kg}$. Given that the collision is elastic, what are the final velocities of the two objects. Neglect friction.

Assertion (A): A body of mass "$\mathrm{m}_1$" collides another body of mass "$\mathrm{m}_2$" at rest elastically. The fraction of energy transferred to the second body is $\frac{m_1}{m_1+m_2}$
Reason (R): In an "inelastic collision" both linear momentum and KE is conserved

A body is revolving with a uniform speed v in a circle of radius $r$. The tangential acceleration is

Statement-1: A body of mass 5 kg is placed on a moving car
having velocity 4 m/s. The kinetic energy of the block is 40 J in all
frames.
Statement-2: The kinetic energy of a system or body is different
in different frames.

A string of length $0.1 \mathrm{~m}$ cannot bear a tension more than $100 \mathrm{~N}$. It is tied to a body of mass $100 \mathrm{~g}$ and rotated in a horizontal circle. The maximum angular velocity can be

Work done by friction in case of pure rolling

In which case does the potential energy decrease

Assertion: Linear momentum of a system of particles is zero.
Reason: Kinetic energy of a system of particles is zero.

A body is being raised to a height $h$ from the surface of earth. What is the sign of work done by applied force and gravitational force respectively?

The minimum speed for a particle at the lowest point of a vertical circle of radius r, to describe the circle is $v$. If the radius of the circle is reduced to one-fourth its value, the corresponding minimum speed will be

Choose the incorrect statement

Suppose the average mass of raindrops is $3 \times 10^{-5} {~kg}$ and their average terminal velocity $9 {~ms}^{-1}$. Then the energy transferred by rain to each square metre of the surface at a place which receives $100 {~cm}$ of rain in a year is

Force acting on a particle moving in a straight line varies with the velocity of the particle as $F=\frac{K}{v}$. Here $K$ is constant. The work done by this force in time $t$ is

A body slides down a frictionless track which ends in a circular loop of diameter D. Then the minimum height h of the body in terms of D so that it may just complete the loop, is

A bullet of mass $20 \mathrm{~g}$ moving with $600 \mathrm{~ms}^{-1}$ collides with a block of mass $4 \mathrm{~kg}$ hanging with the string of length $0.4 \mathrm{~m}$. What is velocity of bullet when it comes out of block, if block rises to height $0.2 \mathrm{~m}$ after collision? (Take, $g=10 \mathrm{~ms}^{-2}$ )

The string of a pendulum of length l is displaced through ${90^0}$ from the vertical and released. Then the minimum strength of the string in order to withstand the tension as the pendulum passes through the mean position is