Work Energy and...

A position dependent force $$F = 7 - 2x + 3x^2$$ newton acts on a small body of mass $$2 kg$$ and displaces it from $$x = 0$$ to $$x = 5$$. The work done in joule is :

$$\overrightarrow { F }  =x\hat i+y\hat j$$, is this force:

 A force of $$1200 \mathrm { N }$$ acting on a stone by means of a rope slides the stone through a distance{ of$$ 10 \mathrm { m }$$in a direction inclined at $$ 60 ^ { \circ } $$ force. The work done by the force is

$$\begin{array} { l } { \text { A man weighing } 80 \mathrm { kg } \text { climbs a staircase } } \\ { \text { carrying a } 20 \mathrm { kg } \text { load. The staircase has } 40 } \\ { \text { steps, each of } 25 \mathrm { cm } \text { height. If he takes } 20 } \\ { \text { seconds to climb, the work done is } } \end{array}$$

Five identical balls each of mass m and radius r are strung like beads at random and at rest along a smooth, rigid horizontal thin rod of length L, mounted between immovable supports. Assume $$10r<L$$ and that the collision between balls or between balls and supports are elastic. If one ball is struck horizontally so as to acquire a speed v, the average force felt by the support is 

The displacement (x) and time (t) for a particle are related as $$t=\sqrt { x } +3$$. What is the work done in the first six second of its motion?

When a 4 kg mass is hung vertically on a light spring obey's Hooks law , the spring stretches by 2 cms. The work required to be done by an external agent in stretching this spring by 5 cm will be ( g =9.8 $${ ms }^{ -2 }$$ )

A variable force given by $$ F= ( 3x^2 \hat i + 4 \hat j) $$ acts on a particle. the force is in newton and x is in meter. what is the change in KE of particle as it moves from point (2, 3) to (3, 0) 

A particle moves along positive X-axis from x=$$0$$ to x=$$5$$ under influence of force is given by$$F={ x }^{ 2 }-2x-8.$$ The work done by the force is 

Two bodies of masses $$4kg$$ and $$16kg$$ are at rest. The ratio of times for which the same force must act on them to produce the same kinetic energy in both of them is