A) 800 N
B) 1200 N
C) Zero
D) 400 N
Correct Answer: B
Solution :
Key Idea: When lift is moving upwards, it weighs more than actual weight of man by a factor of ma. |
Mass of man \[M=80\text{ }kg\] |
Acceleration of lift, \[a=5\text{ }m/{{s}^{2}}\] |
When lift is moving upwards, the reading of weighing scale will be equal to R. The equation of motion gives |
\[R-Mg=Ma\] |
or \[R=Mg+Ma=M(g+a)\] |
\[\therefore \] \[R=80(10+5)=80\times 15=1200\,N\] |
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