Work and Energy...

An object is dropped from height $$h=2R$$ on the surface of earth. Find the speed with which it will collide with ground, by neglecting effect of air. [$$R$$ is radius of earth. Take mass of earth as $$M$$]

The mass of object X is $$M_1$$ and that of object Y is $$M_2$$. Keeping their kinetic energy constant, if the velocity of object Y is doubled the velocity of object X, what will be the relation between their masses?

A car weighing 1 ton is moving twice as fast as another car weighing 2 ton. The kinetic energy of the one-ton car is

The work function of tungsten is $$4.50eV$$. The wavelength of fastest electron emitted when light whose photon energy is $$5.50eV$$ falls on tungsten surface, is

Two riffles fire the same number of bullets in a given interval of time. The second fires bullets of mass twice that fired by the first and with a velocity that is half that of the first. The ratio of their powers is?

Refer above figure.

A pump of $$200W$$ power is lifting $$2kg$$ water from an average depth of $$10m$$ in one second. Velocity of water delivered by the pump is :

A man raises 1 kg wt. to a height of 100 cm and holds it there for 30 minutes. How much work has he performed?

A skater of weight $$30 \ kg$$ has initial speed $$32m/s$$ and second one of weight $$40 \ kg$$ has $$5m/s$$. After the collision, they stick together and have a speed $$5m/s$$. Then the loss in KE is

Two bodies A and B have masses $$20\ kg$$ 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 $$\dfrac { t_{ A } }{ t_{ B } } $$: