Work Energy and...

does not vary from point to point in space Which pair of the following forces will never give resultant force of 2 N?

The speed of a motor increases from 1200 rpm to 1800 rpm in 20 s. How many revolutions does it make during these second?

A hollow smooth uniform sphere $$A$$ of mass $$m$$ rolls without sliding on a smooth horizontal surface. It collides elastically and head-on with another stationary smooth hollow sphere $$B$$ of the same mass mm and same radius. The ratio of the kinetic energy of $$B$$ to that of $$A$$ just after the collision is 

AB is long frictionless horizontal surface. One end of an ideal spring of spring constant K is attached to a block of mass m, which is being moved left moved left with constant velocity v, and another end is free.Another block of mass 2m is given a velocity 3v towards the spring. Work done by an external agent in moving m with constant velocity v in a long time will be:

The work done by a force $$F=(-6x^3\hat
i)$$ in displacing a particle from $$x = 4m$$ to $$x = -2m$$ is:     

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

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

Work done by air when it expands from 50 litres to 150 litres at a constant pressure of 2 atmospheres is:

A block of mass 10 kg is moving up on an inclined plane with constant acceleration 2 m/sec by applying a constant force F as shown in the fig. The work done on the block by applied force F in 2 s is

A force $$\vec { F } =\left( { 3x }^{ 2 }+2x-7 \right) $$ N acts on a 2 kg body as a result of which the body gest displaced x=0 to x=5 cm. The work done by the force will be-