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  • A block of mass 5kg, kept on a moving plateform is being observed by a person standing on the same plateform. The plateform is moving upwards and its velocity time graph is given in the figure belo

A block of mass 5kg, kept on a moving plateform is being observed by a person standing on the same plateform. The plateform is moving upwards and its velocity time graph is given in the figure below. The ratio of apparent weight of the block as observed by the man at t=1sec and t=3 sec.(g=10m/s2)

Option: 1

\frac{1}{3}


Option: 2

3


Option: 3

2


Option: 4

1


Answers (1)

best_answer

Given-

Mass of block, m=5kg,

Let upward acceleration of block be 'a' and reaction force on the block by platform be 'R'. The apparent weight of the block is equal to the reaction force on the block.

F.B.D of the block-

\\ R-mg=ma\\ \Rightarrow R=m(g+a)\ ...(1)

Velocity time graph of block-

The slope of velocity-time graph is acceleration.

Acceleration of block at t=1s-

a_{1}=\frac{20-10}{2-0}=5m/s^2

Acceleration of block at t=3s-

a_{3}=\frac{0-20}{6-2}=-5m/s^2

Apparent weights at t=1s and, t=3s-

\\ R_{1}=m(10+5)\\ R_{3}=m(10-5)\\ \Rightarrow \frac{R_{1}}{R_{3}}=3

Posted by

Gautam harsolia

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