Q. 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
Rajasthan PMTRajasthan PMT 2008Work, Energy and Power
Solution:
The height $ (h) $ traversed by particle while going up is $ h=\frac{{{u}^{2}}}{2\,\,g}=\frac{25}{2\times 9.8} $
Work done by gravity force $ =m\,\,\overset{\to }{\mathop{\mathbf{g}}}\,\cdot \overset{\to }{\mathop{\mathbf{h}}}\, $ $ =0.1\times g\times \frac{25}{2\times 9.8}\cos {{180}^{o}} $ [Angle between force and displacement is $ {{180}^{o}} $ ] $ \therefore $ $ W=-0.1\times \frac{25}{2}=-1.25\,\,J $
