A boy stands on a weighing machine inside a lift. When the lift is going down with acceleration g / 4 , the machine shows a reading 30 kgf. When the lift goes upwards with acceleration g / 4 , the reading would be

Step-by-step solution

While going down, machine reading is 30 kgf . aligned & m g-N=m ( g 4 ) & m g-30 g= m g 4 ; 3 m g 4 =30 g & m= 30 4 3 =40 ~kg aligned While going up, the reaction would be aligned & N^ -m g=m g 4 & N^ =5 m g 4 = 5 4 (40 ~kg ) g N^ & =50 kgf . aligned