Work-energy-power practice · Medium

When a simple pendulum is rotated in a vertical plane with constant angular velocity, centripetal force is

Assertion: When a force of 20 N displaces a body by 5 m then work done by this force must be 100 J for every observer watching that body.
Reason: Work done on a body does not depend on the observer that is observing the body.

A spring when stretched by 2 mm its potential energy becomes 4 J. If it is stretched by 10 mm, its potential energy is equal to

Assertion: During horizontal circular turn of a car, the centripetal force required should be less than
the limiting friction between its tyres and road.

Reason: The centripetal force to car is provided by the frictional force between its tyres and road.

The power of a water jet flowing through an orifice of radius r with velocity v is

Angle between position vector and acceleration vector of a particle in uniform circular motion (centre of circle is taken as origin) is

Consider the following two statements 1. Linear momentum of a system of particles is zero 2. Kinetic energy of a system of particles is zero, Then

Potential energy is also called as

Statement-I: In circular motion, the centripetal and centrifugal force acting in opposite direction balance each other.
Statement-II: Centripetal and centrifugal forces don't act at the same time.

A running man has the same kinetic energy as that of a boy of half his mass. The man speed up by $2\mathrm{\;m}{\mathrm{s}^{ - 1}}$ and the boy changes his speed by $x = \mathrm{m}{\mathrm{s}^{ - 1}}$, so that the kinetic energies of the boy and the man are again equal. Then x in $\mathrm{m}{\mathrm{s}^{ - 1}}$ is

A force $\vec{F}=\frac{-k}{x^2} \hat{i}(x \neq 0)$ acts on a particle moving in $x$-direction. The work done by this force in displacing a particle from $x=+a$ to $x=+2 a$ ( $k=$ Positive constant) is equal to

If the engine power is $3.3 \mathrm{~kW}$ and it is $60 \%$ efficient, how much water will it pump in $5 \mathrm{~s}$ from a height of $10 \mathrm{~m}$ ?

Statement-1: Linear momentum is conserved only during an elastic collision between two finite particles
Statement-2: The collision is infact a redistribution of the total momentum of the particles.

Consider a one-dimensional motion of a particle with total energy $E$. There are four regions $A, B, C$ and $D$ in which the relation between potential energy $V$, kinetic energy $K$ and total energy $E$ is as given below:

Region $A: V > E$

Region $B: V < E$

Region $C: K > E$

Region $D: V > K$

Which of the following regions the particle cannot be found?

Assertion: Kinetic energy is conserved in both, perfectly elastic & inelastic collisions.
Reason: Because both the types of collisions are identical.

A particle is moving in a circle of radius $r$ under the action of a force ${F}=\alpha {r}^2$ which is directed towards centre of the circle. Total mechanical energy (kinetic energy + potential energy) of the particle is (take potential energy $=0$ for $r=0$):

Two bodies A and B have masses 2 kg and 5 kg respectively. Each one is acted upon by a force of 4 kg wt. If they acquire the same kinetic energy in times ${t_A}\,and\,{t_B}$ , then the ratio$\frac{{{t_A}}}{{{t_B}}}$ is

I. In elastic collision, initial kinetic energy is equal to the final kinetic energy.
II. In elastic collision, kinetic energy during the collision time $\Delta t$ is constant.

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

A body of mass 2 kg moves down the quadrant of a circle of radius 4 m. If the velocity on reaching the lowest point is 8 m/s. The work done against friction is

The kinetic energy of a body is increased by $300\%$. What is the percentage increase in the momentum of the body?

Which of the following statements is/are true about the rotatory motion along a circular path?

Statement-1: Work done by conservative force along closed path is zero.
Statement-2: When an object is moved along closed path beginning and ending at same point its displacement is zero.

A bucket full of water weighs 5 kg, it is pulled from a well 20 m deep. There is a small hole in the bucket through which water leaks at a constant rate of $0.2kg{m^{ - 1}}$ .The total work done in pulling the bucket up from the well is ($g = 10m{s^{ - 2}})$

The work done in pulling up a block of iron weighting 2 KN with a constant velocity through a distance of 10 m on a smooth inclined at an angle of $30^\circ$ with the horizontal is $\left[ {g = 10\,\,\,{\text{m}}{{\text{s}}^{ - 2}}} \right]$

If the momentum of a body is increased by 50% then the percentage increase in its kinetic energy is

Statement I Two bodies of different masses have the same momentum, and their kinetic energies are in the inverse ratio of their masses.

Statement II Kinetic energy of body is given by the relation.

${KE}=\frac{1}{2} m v^2$

Consider the following statements. A and B and identify the correct answer given below. I. Body initially at rest is acted upon by a constant force. The rate of change of its kinetic energy varies linearly with time. II. When a body is at rest, it must be in equilibrium.

A marble going at a speed of $2\,\,m/s$ hits another marble of equal mass at rest. If the collision is perfectly elastic, then the velocity of the first marble after collision is $\left( {in\,\,m/s} \right)$

The tension in the string revolving in a vertical circle with a mass m at the end which is the lowest position

If momentum will increase by $0.3 \%$ and mass will decrease by $0.2 \%$, then find out percentage change in kinetic energy.