A particle of mass 100 g is thrown vertically upwards with a speed of 5 m/s. The work done by the force of gravity during the time the particle goes up is
AIEEE Solved Paper-2006
A)\[-0.5J\]
B) \[-1.25\,J\]
C) 1.25 J
D) 0.5 J
Correct Answer:
B
Solution :
The height (^traversed by particle while going up is \[h=\frac{{{u}^{2}}}{2g}=\frac{25}{2\times 9.8}\] Work done by gravity force\[m\,\vec{g}.\vec{h}\] \[=0.1\times g\times \frac{25}{2\times 9.8}\cos {{180}^{o}}\] (angle between force and displacement is\[180{}^\circ \]) \[\therefore \]\[W=-0.1\times \frac{25}{2}=-1.25J\]