| A block of mass m is kept on a platform which starts from rest with constant acceleration \[g/2\] acceleration \[g/2\] upward, as shown in figure. Work done by normal reaction on block in time is-[JEE Main 10-Jan-2019 Morning] |
 |
A) \[\frac{m{{g}^{2}}{{t}^{2}}}{8}\]
B) \[\frac{3\,m{{g}^{2}}{{t}^{2}}}{8}\]
C) \[-\frac{\,m{{g}^{2}}{{t}^{2}}}{8}\]
D) 0
Correct Answer: B
Solution :
| [b] \[N=m\left( g+\frac{g}{2} \right)\,=\,\frac{3mg}{2}\] |
| \[S\,=\,\frac{1}{2}\,\,\times \,\,\frac{g}{2}{{t}^{2}}\] |
| Work done \[=\,\,\frac{3mg}{2}\,\,\times \,\frac{g}{4}{{t}^{2}}\,=\,\frac{3m{{g}^{2}}}{8}{{t}^{2}}\] |
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