Work, Energy & Power Questions

A drop of liquid of diameter 2.8 mm breaks up into 126 identical drops. The increase in energy is nearly equal to (If surface tension = 75 dynes/cm):

An object of mass 5 kg falls from rest through a vertical distance of 20 m and reaches a velocity of 10 m/s. How much magnitude of work is done by the push of the air on the object ? (g = 10 m/s²).

Find out potential energy of the system

Read both the statements carefully and choose the correct alternative. Assertion (A): The instantaneous power developed by a force acting on a body is measured as the dot product of instantaneous velocity of the body and the force acting on it at tha

A quarter horse power motor runs at a speed of 600 r.p.m. Assuming 50% efficiency, the work done by the motor in one rotation will be

A body is suspended from a smooth horizontal nail by a string of length 0.25 metre. What minimum horizontal velocity should be given to it in the lowest position so that it may move in a complete vertical circle with the nail at the centre ?

An insect is crawling in a hemi-spherical bowl of radius R. If the coefficient of friction between the insect and bowl is μ , then the maximum height to which the insect can crawl the bowl is

An elevator has a fully loaded mass of 1200 kg. It moves upward at a constant speed of 2.5 m s−1. If a constant frictional drag of 3000 N opposes its motion, determine the minimum power the motor must deliver. (Assume g = 10 m s−2)

A stone projected up with velocity u reaches a maximum height h. When it is at a height of 3h/4 from the ground, the ratio of KE and PE at that point is:

A body moves a distance of 10 m along a straight line under the action of a force of 5 N. If the work done is 25 joule, the angle which the force makes with the direction of motion of the body is:

A 2 kg mass lying on a smooth horizontal table is displaced in the horizontal direction by 50 cm. The work done by the normal reaction on the mass will be:

If the kinetic energy of a moving body is increased to 16 times of its original value, then the linear momentum will increase by:

The position of a particle of mass 4 g, acted upon by a constant force is given by x = 4t² + t, where x is in metre and t in second. The work done during the first 2 seconds is:

Most appropriate graph between kinetic energy E and velocity V is:

A cord is used to lower vertically a block of mass M by a distance d at a constant downward acceleration of g/4. Then the work done by the cord on the block is:

A particle of mass m is driven by a machine that delivers a constant power k watt. If the particle starts from rest the force on the particle at time t is:

A particle in a certain conservative force field has a potential energy given by U = 20xy/z. The conservative force acting on it is:

The potential energy U varies with the position x of a particle according to relation U(x) = (x² − 6x) J (where x is in meter). Choose the correct option.

A stone of mass 0.2 kg is tied to one end of a thread of length 0.1 m whirled in a vertical circle. When the stone is at the lowest point of circle, tension in thread is 52 N. The kinetic energy of the stone at the lowest point is: (g = 10 m/s²)

A mass m is attached to a string and revolves in a vertical circle with a radius r. If the speed of the mass at its lowest point is v, what is the tension in the string at that position?

A force F = (x + 1) N acts on a particle in x-direction. What is the work done by this force in displacing a particle from x = 1 m to x = 2 m?

Force constants of two ideal springs S₁ and S₂ are in the ratio 3 : 2. They are stretched by the same lengths separately. If the potential energy stored in first spring S₁ is 10 J, then the potential energy stored in the spring S₂ is:

Potential energy of a body at position A is −40 J. Work done by conservative forces in moving the body from A to B is −20 J. Find the potential energy of the body at position B.

Which of the following statement is incorrect for a conservative force field?

A car is moving at a speed of 40 km/hr. If the car engine generates constant 7 kilowatt power, then the resistive force in the path of motion of the car is:

Internal forces acting within a system of particles can alter:

A car of mass m starts from rest and accelerates so that instantaneous power delivered to the car has a constant magnitude P₀. The instantaneous velocity of this car is proportional to: (t is time)

A block of mass 5 kg slides down from rest on a rough surface having 30° inclination with horizontal. If the heat loss due to friction is 75 J, the kinetic energy gained by the block on descending a height of 10 m is: (g = 10 m/s²)

The relation between a conservative force F and potential energy U is given by: (x is the displacement caused by force F)

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R: Assertion (A): A spring has potential energy, both when it is compressed or stretched. Reason (R): In compressing or stretching, work is done on the

Two bodies of masses m₁ and m₂ have equal kinetic energies. If p₁ and p₂ are their respective momentum, then ratio p₁ : p₂ is equal to:

An engine pumps water through a hose pipe. Water passes through the pipe and leaves it with a velocity of 2 m/s. The mass per unit length of water in the pipe is 100 kg/m. What is the power of the engine?

A force F = (3x² + 2x − 7) N acts on a 2 kg body as a result of which the body gets displaced from x = 0 to x = 5 m. The work done by the force will be:

The potential energy of a 2 kg particle, free to move along x-axis is given by V(x) = (x³/3 − x²/2) J. The total mechanical energy of the particle is 4 J. Maximum speed (in ms⁻¹) is:

When a force retards the motion of body, the work done is:

A crate is pushed horizontally with 100 N force across a 5 m floor. If the frictional force between the crate and the floor is 40 N, then the kinetic energy gained by the crate is:

In a conservative field, the potential energy U as a function of position x is given by U = x². Then the corresponding conservative force is given by:

If a body of mass 2 kg is moving with constant velocity of 2 m/s, then the kinetic energy of the body is:

If a machine gun fires n bullets per second each with kinetic energy K, then the power of the machine gun is:

Two springs with spring constant k₁ = 1500 N/m and k₂ = 3000 N/m are stretched by the same force separately. The ratio of potential energies stored in the springs U₁/U₂ will be:

A body is dropped from a height h in the absence of all dissipative forces. When velocity of body is v, the loss in its potential energy is U. The mass of the body is:

A stone of mass m, tied to a string is being whirled in a vertical circle such that stone just completes the circle. The tension in the string is:

Given below are two statements: Statement I: The work done on a particle by a conservative force is independent of the path taken by the particle. Statement II: Kinetic energy is independent of the reference frame. In the light of the above statement